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LeafLabs Garden » Recent Posts http://forums.leaflabs.com/ A place to share, learn, and grow... en-US Wed, 22 May 2013 15:00:14 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://forums.leaflabs.com/search.php feurig on "re-flash bootloader bin, but still cannot use USB drivers for DFU" http://forums.leaflabs.com/topic.php?id=11729#post-26117 Tue, 21 May 2013 20:03:02 +0000 feurig 26117@http://forums.leaflabs.com/ Windows? NORSTAR on "re-flash bootloader bin, but still cannot use USB drivers for DFU" http://forums.leaflabs.com/topic.php?id=11729#post-26112 Tue, 21 May 2013 10:48:13 +0000 NORSTAR 26112@http://forums.leaflabs.com/ I had somehow wiped out the bootload utility on the board (Lost all LEDS and could not communicate). I used an Orangutan SVP1248 to communicate with the Flymaple (RET6) through its TTL com port and followed the "re-flash bootloader program." Windows recognised the board as "Maple." Finally, I was able to download "Blink" and have it running again. I'd hoped the Flymaple board would go back to the original utility that would allow me to download the programs using only a USB cable, but 1) The board will not find the DFU, 2) the board still does not go into perpetual boatload mode. When I try to go to perpetual bootload mode, it doesn't seem to stay in the mode and simple goes back to running the "Blink" program. Is the board going to have always be programmed through the Orangutan, or have I skipped something? Perhaps the ROM that hold the bootloader program is corrupted? Any help would be greatly appreciated. siy on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26107 Tue, 21 May 2013 05:00:39 +0000 siy 26107@http://forums.leaflabs.com/ @gbullmer, some time ago I wrote an article (<a href="http://we.easyelectronics.ru/evsi/izgotovlenie-trafaretov-dlya-naneseniya-payalnoy-pasty.html" rel="nofollow">http://we.easyelectronics.ru/evsi/izgotovlenie-trafaretov-dlya-naneseniya-payalnoy-pasty.html</a>) about making stencils from aluminium cans where process described in details (with pictures). This article is in Russian, but I'm going to post (translated, of course) version of this article at Instructables. Can't promise more or less precise time frame because other project (current source for through hole plating) takes almost all my spare time. stafil on "Serialx.read() on Maple behaves different than on Arduino" http://forums.leaflabs.com/topic.php?id=1174#post-26106 Tue, 21 May 2013 01:40:09 +0000 stafil 26106@http://forums.leaflabs.com/ i work with code with maple r5, maple 0.0.12, on win8pro: <pre><code>void setup() { Serial2.begin(9600); } void echoCharacter() { // Check to see if we have received any information. numUnread // will hold the number of bytes we've received, but haven't // looked at yet. int numUnread = Serial2.available(); // numUnread > 0 means that there are some unread bytes waiting if (numUnread > 0) { // Read a single byte out: byte b = Serial2.read(); // And then print it back: Serial2.print(b); } } void loop() { echoCharacter(); }</code></pre> after send 186 chars from pc stm32 is stopped working. gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26104 Mon, 20 May 2013 19:32:24 +0000 gbulmer 26104@http://forums.leaflabs.com/ I've pushed an update introducing Orone-mini-S8E: <a href="https://github.com/gbulmer/openstm32hw/tree/master/Orone-mini-v0/Orone-mini-S8E-v0r001" rel="nofollow">https://github.com/gbulmer/openstm32hw/tree/master/Orone-mini-v0/Orone-mini-S8E-v0r001</a> 1. Added 2pin 0.1" pitch header for USB 'DISC' and ground. This moved the 'DISC' pad off the 0.1" grid, used for all other pads, to find enough space to add the ground pin 0.1" away from it. This is intended to ease manual control of the USB pull-up resistor (R-up), and hence help folks to use the STM32F303's manufactured-in USB bootloader. This change is physically incompatible with Orone-mini-S8D, and other Orone-mini's. Hence it is a new 'part number' There are other small changes: 2. Increased clearance between STM32F and decoupling capacitors, responding to soycamo's feedback about assembly problems 3. Added 'usb only' warning to 'User top' (Eagle bottom) silk screen around USB pins, addressing soycamo's (and my) concerns about misuse of USB D+/D- as GPIO via header pins 4. Added 'ain' and 'pwm' identification for header pins on 'User top' (Eagle bottom) silk screen 5. Minor 'tidy-up' of 'User top' (Eagle bottom) silk screen 6. Increased separation between analogue ground (AGND) and other signals, intended to reduce the ADC noise signal, responding to ventosus' helpful ADC noise measurements (of course, this needs to be tested) 7. Updated 'README' to show which Orone-mini designs have been 'superseded', and hence are not likely to be updated and improved. gbulmer on "Serialx.read() on Maple behaves different than on Arduino" http://forums.leaflabs.com/topic.php?id=1174#post-26102 Mon, 20 May 2013 16:35:37 +0000 gbulmer 26102@http://forums.leaflabs.com/ stafil - Would you please post the programs (on pastebin or gist if it is quite long) for us to see? It is very difficult to guess what the problem might be otherwise. stafil on "Serialx.read() on Maple behaves different than on Arduino" http://forums.leaflabs.com/topic.php?id=1174#post-26101 Mon, 20 May 2013 16:29:49 +0000 stafil 26101@http://forums.leaflabs.com/ I send from PC 178 characters to maple r5 and i receive 129 chars. gbulmer on "Serialx.read() on Maple behaves different than on Arduino" http://forums.leaflabs.com/topic.php?id=1174#post-26100 Mon, 20 May 2013 14:26:39 +0000 gbulmer 26100@http://forums.leaflabs.com/ stafil - "How I read buffer with 200 chars length? HardwareSerial::read(void) read only 64." <code>uint8 HardwareSerial::read(void)</code> reads and returns one character at a time. So I don't understand your question. Would you please post an example program (on pastebin or gist if it is quite long) for us to see? stafil on "Serialx.read() on Maple behaves different than on Arduino" http://forums.leaflabs.com/topic.php?id=1174#post-26099 Mon, 20 May 2013 12:49:58 +0000 stafil 26099@http://forums.leaflabs.com/ How I read buffer with 200 chars length? HardwareSerial::read(void) read only 64. thx gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26098 Mon, 20 May 2013 09:14:56 +0000 gbulmer 26098@http://forums.leaflabs.com/ siy - Thank you for sharing the trick needed to flatten aluminium sheets from cans. There are likely a bunch of folks who will try that. AFAICT most secondary schools in my part of the UK either have a laser cutter, or can get access to a laser cutter at a nearby school. I don't know if they keep it well-enough aligned to cut stencils, so etching a stencil might be an important alternative. gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26096 Mon, 20 May 2013 07:34:34 +0000 gbulmer 26096@http://forums.leaflabs.com/ ala42 - "I do not use the chip internal pullup for the F4, as it requires to use PA9 to connect to VBUS, ..." Thank you very much for that pearl of wisdom. That's a valuable improvement in my understanding. "... so PA9 can not be used for USART1." The person assigning functions to pins had an "off day" with that. That damages the ability to use USART1 for booting. IMHO that was a poor decision because USART1 is the only common boot peripheral across all the STM32F's :-( "My USB port needs an external pullup." Okay. Conclusion: USB_DISC needs to be available on a pad as a signal to control R-up even on an STM32F4. siy on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26093 Mon, 20 May 2013 04:43:47 +0000 siy 26093@http://forums.leaflabs.com/ @gbullmer, sorry for delays, I was busy with other project and had no time to look here. <blockquote> siy - Making the solder paste stencil using etching is a good suggestion. However, I am concerned on a few areas: 1. I would prefer to use a technique that is easy for hardware beginners to use without my involvement. I actually think more people have access to laser cutters than to etching equipment (in the UK). I think folks often use pre-coated photoresist which doesn't need developer. AFAIK, dry film photoresist uses a developer. Is that correct? </blockquote> Well, both photoresists need a developer. Dry film photoresist uses water solution of sodium carbonate (~1% by weight). This one is quite safe by all means (it's widely used for softening water and other purposes, it even registered as food additive E500). About etching equipment: for this purpose you don't need any special etching equipment other than you need for PCB's (etching solution is the same). About laser cutters: they are quite rare here and tray with ferric chloride is much more accessible than laser cutter. <blockquote> 2. Might using cans as raw material a bit too challenging for schools? I would be worried that folks would cut themselves. Is there a good way to make handling the can easy and safe? </blockquote> Cutting cans is quite safe operation. If you think this might present a danger for schools, they can wear gloves before cutting (I'd suggest to do so at least initially). <blockquote>Using thin aluminium sheet with a nice rounded edge might be okay. </blockquote> Yes, that definitely better especially because aluminium cans need additional processing before use: paint at both sides of aluminium sheet cut from can need to be removed with fine grained sand paper and to make sheet flat it need to be put into oven with some weight on top of it and then heated to about 220-250 degrees and slowly cooled. So, using ready to use thin aluminium sheet is definitely better. I'm using cans just because they are easy to find here (unlike aluminium sheet of required thinckness). TheAceOfHearts on "Laser Tag Revolution, showing off a project I worked all semester on!" http://forums.leaflabs.com/topic.php?id=11692#post-26092 Mon, 20 May 2013 01:47:54 +0000 TheAceOfHearts 26092@http://forums.leaflabs.com/ cesarandreu You can find it here: <a href="https://github.com/cesarandreu/laser_tag_reloaded" rel="nofollow">https://github.com/cesarandreu/laser_tag_reloaded</a> :D ala42 on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26089 Sun, 19 May 2013 17:01:54 +0000 ala42 26089@http://forums.leaflabs.com/ > I was trying to minimise hacking on the USB libraries, which I assumed used the on-board R-up (I didn't check) I do not use the chip internal pullup for the F4, as it requires to use PA9 to connect to VBUS, so PA9 can not be used for USART1. My USB port needs an external pullup. gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26088 Sun, 19 May 2013 15:34:42 +0000 gbulmer 26088@http://forums.leaflabs.com/ soycamo - <blockquote>For example the Semtech EClamp2522P looks perfect, ... Unfortunately, the ground connection is a pad under the chip. I am not confident that a newbie (or me) could make that using simple SMD techniques, ... Looking at the footprint, I can see why you would hesitate with this part. I'm willing to give it a shot. If you're cutting soldermasks with a laser cutter, the difference seems negligible. If you're doing SMT by hand... well... :( </blockquote> To be clear, I don't plan on changing to use EClamp2522P in the near future. I think that 'easy to make solder paste stencils' is a pre-requisite to using chips like that, with pads completely under the body. <blockquote>I could put solder bridges in the USB D+/D- tracks so that the header pins are normally not connected. That seems preferable but yeah, that would be a feat. I suppose you could move the solder bridge to the other side? (Pretending that it makes sense electrically, I would.) </blockquote> Yes, if I did add solder bridges to connect the USB signals to header pins, they would be on the (Eagle) bottom copper, user 'top'. "Another concern I have related to assembly is the position of the caps near the microcontroller ... It made rework pretty hard. I forked the repo and had started moving things around so I can show you what I think is a more optimal position for the caps, from an "I'm a novice at SMT" perspective." Excellent point. I'd be very pleased to see that. It feels like the design is stabilising, so I should also ask Chris Evans to have a hard look. When we did the old Orone board, he said that some caps were too close, and made assembly and rework hard. I'd forgotten about that, so thank you for raising that issue. Maybe making the board a mm or two longer would help create plenty of space? I'm so happy you found the through-hole USB part. I am very pleased that you like it too. I was surprised how time consuming finding it was (carried by 5 of 6 distributors I use). However it feels like time well spent. I do like 'over-engineered' sockets and connectors; they often take the strain :-) soycamo on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26087 Sun, 19 May 2013 13:38:27 +0000 soycamo 26087@http://forums.leaflabs.com/ @gbulmer For example the Semtech EClamp2522P looks perfect, though it is still 1.6mm x 1.6mm. The USB R-up is controlled by a separate pin, and isn't wired directly to Vusb. Unfortunately, the ground connection is a pad under the chip. I am not confident that a newbie (or me) could make that using simple SMD techniques, and I think it'd be awkward to diagnose the defect and fix it. Looking at the footprint, I can see why you would hesitate with this part. I'm willing to give it a shot. If you're cutting soldermasks with a laser cutter, the difference seems negligible. If you're doing SMT by hand... well... :( I could put solder bridges in the USB D+/D- tracks so that the header pins are normally not connected. That seems preferable but yeah, that would be a feat. I suppose you could move the solder bridge to the other side? (Pretending that it makes sense electrically, I would.) Another concern I have related to assembly is the position of the caps near the microcontroller -- I put way too much paste on the board so there were some shorts. My friend and I were able to clean up most of them except for around the microcontroller. It made rework pretty hard. I forked the repo and had started moving things around so I can show you what I think is a more optimal position for the caps, from an "I'm a novice at SMT" perspective. I'm so happy you found the through-hole USB part. Again, thanks for all your work! gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26086 Sun, 19 May 2013 11:22:42 +0000 gbulmer 26086@http://forums.leaflabs.com/ soycamo - Thank you for the comments. "We were using this part for the Maple Bacon: STF202" That is the chip Siy uses for USB termination and ESD protection. AFAIK, based on a post be feurig, that is where Maple bacon took that part of its schematic. For me, the NUF2042XV6 has a few advantages over the STF202. To make my boards easier to make, I try to restrict them to SMD on one side only. I like this approach a lot (we used it on the OU's SenseBoard, but not fully). This makes DIY SMD simpler. For example, it lets folks use the SMD reflow 'skillet' technique. To make the USB socket connection more robust the USB socket is thru-hole. To get more space for SMD, and more space for user silk screen, the USB socket in on the non-SMD side, along with all of the users silk screen. So thru-hole USB sockets are my favoured approach. The pinout of the NUF2042XV6 is easy to route to the thru-hole USB socket. The STF202 seems a better fit with SMD USB sockets. Before doing the mini, I had been playing with a design for a 64pin LQFP STM32F103/STM32F4 board. STM32F2 and STM32F4 have USB pull-up resistors built into the chips full-speed USB peripheral, so I thought they could skip external pull-up resistor circuitry. Hence the NUF2042XV6 seems ideal; the pull-up parts can be omitted for STM32F4, and it should work correctly. However, it is more messy to use the STF202 with STM32F4; either the Vusb input signal can't be connected, and hence Vusb can't be ESD protected, or the on-board R-up mustn't be used. I was trying to minimise hacking on the USB libraries, which I assumed used the on-board R-up (I didn't check) so I chose to use the NUF2042XV6. AFAIK, the only 48pin STM32F4 is the STM32F401, and I haven't even looked to see if it would be easy to modify Orone-mini for it, so it isn't yet an import consideration. There are a few other USB termination and ESD parts. For example the Semtech EClamp2522P looks perfect, though it is still 1.6mm x 1.6mm. The USB R-up is controlled by a separate pin, and isn't wired directly to Vusb. Unfortunately, the ground connection is a pad under the chip. I am not confident that a newbie (or me) could make that using simple SMD techniques, and I think it'd be awkward to diagnose the defect and fix it. I might change my view if SMD solder paste templates are easy to make. "One thing that has bothered me that I wanted to fix on my own board is the USB-connected pins. After @feurig gave a class on using the Maple, a student came by a local gathering to explain that he thought he had bricked his Maple Bacon, only for @feurig to discover that it was because of using the pins connected to USB." Yes that is a serious concern that I share. "Soooo we should ax those. However, I'd like to hear arguments on keeping the pins around (or maybe making those pins be optional somehow?" I don't want to remove the USB D+ or D- signals from the pin header because: 1. the Orone-mini is no longer Maple-mini compatible (on the pin-outs they share) 2. If the Orone-mini is used in a design which doesn't use USB, then those two pins can be used as normal I/O. It seems a shame to waste them. It seems like removing those pins penalises the smart to protect the ignorant (or worse), which is not a principle I like to encourage. I would hope the person who made the mistake learned something quite valuable, and that's one of the aims. My 64pin designs don't put USB D+/D- signals on header pins because I/O seems less precious than on the mini, and I am trying to cram into a limited number of pins. To reduce the problem of the USB pins being used by accident, I am planning changes to the silk screen. The silk screen still needs improving anyway (ADC, PWM), so warning that two pins are USB seems to be a good improvement. Anyone have an Eagle library part for a 'skull and crossbones" or a "Warning" sign? I could put solder bridges in the USB D+/D- tracks so that the header pins are normally not connected. However, it is a small board and I'm trying to keep the ground plane as big as practical. Also I believe the USB signals should be simple and direct, with no 'stubs', and bridges with 'optional' tracks would create 'stubs'. So I am less enthusiastic about that than leaving those as they are. I am still open to persuasion. soycamo on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26085 Sat, 18 May 2013 22:13:05 +0000 soycamo 26085@http://forums.leaflabs.com/ @gbulmer I preferred that circuit to Siy's approach. It is a lovely little chip because it contains the USB termination, and ESD protection, without the pull-up resistor. We were using this part for the Maple Bacon: <a href="http://www.onsemi.com/pub_link/Collateral/STF202-22T1-D.PDF">STF202</a> which is slightly bigger than the one you are using but surprisingly similar, though the markings are STILL hard to read. Gosh dang I guess you can't get ESDs any bigger :( That uses 0805. I might like to rework to use the ground-on-tab regulator. I might even be able to fit the extra pads on a longer board, but retain the 0.6" header pin spacing. What do you think? I like that idea, I'm just not sure how time-consuming it will be to keep various versions of these boards around (unless that's not a factor). Does anyone want any changes to the pin out, or can I assume this is the pin-out which we are all (mostly) happy with? One thing that has bothered me that I wanted to fix on my own board is the USB-connected pins. After @feurig gave a class on using the Maple, a student came by a local gathering to explain that he thought he had bricked his Maple Bacon, only for @feurig to discover that it was because of using the pins connected to USB. Soooo we should ax those. However, I'd like to hear arguments on keeping the pins around (or maybe making those pins be optional somehow? gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26081 Sat, 18 May 2013 08:39:11 +0000 gbulmer 26081@http://forums.leaflabs.com/ soycamo - " You use the leftover X-ray sheets like you would kapton sheets. It's simply reusing existing materials." Clever! Maybe I'll try local dentists to get some. Folks are usually extremly helpful when I explain I'm try to help kids make things. Building the Orone-mini-S8A right now... it's in the oven! BRILLIANT! WOW that ESD is super small. Yes. Sorry. I preferred that circuit to Siy's approach. It is a lovely little chip because it contains the USB termination, and ESD protection, without the pull-up resistor. So it is ideal for the STM32F2 and STM32F4 which contains the USB pull-up resistor on-chip. I had hoped the STM32F303 would have that feature too, but sadly not. AFAICT the ESD's only weakness is the small package. " I think 1206 was a bit overkill -- I think I would prefer 0805. It makes an easier "pull" when applying the solder paste." I started with 0805, but then went 1206 because my TekWizz chums thought that would be easier to make. Also local schools used 1206 for SMD beginners. So I have visions of 13yo's making their own "iPods" based on STM32F303 Orone-mini :-) I still have the older design, which is exactly Maple-mini 0.6" header spacing and footprint, except for av+. That uses 0805. I might like to rework to use the ground-on-tab regulator. I might even be able to fit the extra pads on a longer board, but retain the 0.6" header pin spacing. What do you think? However, I think you did a great job on the repo itself, it was very thorough. Thank you very much :-) Folks gave lots of very helpful advice and feedback, so I tried to do an adequate job. I feel it is a good example of the benefit of Open Source hardware. I would look into using tags or branches for various versions I was trying to follow a 'form, fit or function' rule for different versions. So I thought, especially while it is 'in-flight', different pin-outs, different BoM, different track/space needed a different part-number, otherwise it might be a PITA. If we can settle on a pin-out then I think there are still variants which need unique "part numbers", and hence aren't simply tags on the same branch. IMHO track/space variation, e.g. 6mil vs 8mil, need to be a different part number because it matters when making the PCB. I also think BoM variation needs a different part number too. When the PCB is distinct for a BoM or manufacturing purpose it seems better to make them explicit part variants with their own part number. Then only use versions/revisions at the git level to track changes to what should then be 'the same thing'. I like the 43 pin S8D/S8H which puts the LED pin 33, 'Vusb' after the polyfuse, and 'Vx' after the diodes, and USB_DISC on an internal pad. They all seem to be useful. I haven't put USB_DISC in-line with the pin headers because there is no space! Does anyone want any changes to the pin out, or can I assume this is the pin-out which we are all (mostly) happy with? I can see there is an argument for putting av+ back on the header, and by my part-numbering rules, that would be a variant. However, I don't think most people would mind which they use because it should have minimal impact on USB-powered form, fit or function. gbulmer on "WM8762 DAC" http://forums.leaflabs.com/topic.php?id=11698#post-26080 Sat, 18 May 2013 07:38:01 +0000 gbulmer 26080@http://forums.leaflabs.com/ pyrohaz - "The sample rate is actually currently at 45kHz, meaning a prescaler of 1600 (72e6/45e3), since 48kHz is a standard audio sample rate and can be achieved with a prescaler of 1500, I thought that this would be a better value to choose." Okay. So you would be okay getting close, but don't need 48KHz exactly. "If I changed the crystal, would this also give me an increased system clock by 1.5x(ish) to about 111MHz? The system clock speed is set by software, so the CPU could still run at 72MHz. I vaguely remember someone (at LeaLabs) did do an overclock of the Maple by changing the system clock multiplier, but I can't remember what speed they reached. Edit: However, unless you change the bootloader, and flash a new one onto your Maple, it would try to run at 9x11.288MHz, which might not work. I should have been clear about that. "I like the look of the codec shield but i'm looking to do it on the ultimate cheap, the chip I linked above can be picked up for about £3 and comes in a soic8 package which is easily solderable." I like to keep costs low to minimise "barriers to entry". The WM8731 can be bought for £2.82+VAT <a href="http://uk.farnell.com/wolfson-microelectronics/wm8731seds-rv/dac-audio-24bit-headphone-28ssop/dp/1776264" rel="nofollow">http://uk.farnell.com/wolfson-microelectronics/wm8731seds-rv/dac-audio-24bit-headphone-28ssop/dp/1776264</a> Apparently, it can generate its own clocks from a 12MHz signal, so it might be possible to hook it directly to a Maple timer output, set to divide the system clock by 6. But you would need a PCB. If I were doing that, I'd probably include a 12MHz crystal, and local power supply smoothing and decoupling. I might use the Arduino Audio shield PCB, or use it as a starting point, but make it Maple specific by removing some Arduino interface stuff. Irritatingly matching the Arduino shield footprint needs a bit over 50mm wide board, which pushes up the PCB cost (at seeed) a lot, so I might try to squeeze it into 50mm x 50mm. The electronics are probably well under £10. soycamo on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=9#post-26079 Sat, 18 May 2013 00:04:30 +0000 soycamo 26079@http://forums.leaflabs.com/ @gbulmer You use the leftover X-ray sheets like you would kapton sheets. It's simply reusing existing materials. Building the Orone-mini-S8A right now... it's in the oven! I see some discrepancies between what @feurig ordered, the BOM I used to make the parts order, and what's in the github repo. WOW that ESD is super small. I think 1206 was a bit overkill -- I think I would prefer 0805. It makes an easier "pull" when applying the solder paste. I'll give a better update once I've finished. However, I think you did a great job on the repo itself, it was very thorough. I would look into using tags or branches for various versions, but otherwise just cloning the whole thing before I went into the lab worked out great. :D pyrohaz on "WM8762 DAC" http://forums.leaflabs.com/topic.php?id=11698#post-26078 Fri, 17 May 2013 22:28:12 +0000 pyrohaz 26078@http://forums.leaflabs.com/ Cheers for both the replies, If I run it at 125fs, won't it constantly go in and out the expected cycles for the chip? Therefore producing a dodgy output? How can I work out the current error produced by my mismatched resistors? Well i'm using DDS to produce my output waveform with a 12bit wavetable containing 16bit amplitude values. The sample rate is actually currently at 45kHz, meaning a prescaler of 1600 (72e6/45e3), since 48kHz is a standard audio sample rate and can be achieved with a prescaler of 1500, I thought that this would be a better value to choose. If I changed the crystal, would this also give me an increased system clock by 1.5x(ish) to about 111MHz? I like the look of the codec shield but i'm looking to do it on the ultimate cheap, the chip I linked above can be picked up for about £3 and comes in a soic8 package which is easily solderable. Are there any other well priced 16bit dacs? I was looking at the AD1851N but I can only really find it from HK and don't really have time to wait for it to come. Has anyone used the TDA1543 chip either? They seem to be abundant and extremely cheap on ebay too. gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=8#post-26077 Fri, 17 May 2013 17:03:13 +0000 gbulmer 26077@http://forums.leaflabs.com/ ventosus - "... In engraving mode however, the laser cutter acts as a printer. ..." Okay, if that is what "printing" meant, I understand. I don't agree with the nomenclature, though. I happily call the two effects cutting/plotting or engraving, or even raster drawing. I did wonder if the old dental x-ray film was being exposed by the laser, and then used in some sneaky way. We tried using the laser cutter with filled rasters, but found using it as a vector cutter worked better, but still not 'perfect'. So your results are very helpful. Thank you for the values. I'll try to give them a try next week. It would be great to find a way to make low-cost solder paste stencils. I created a DXF for the 'cream' layer, and there are holes in it for the 'lugs' for the Molex USB-mini socket. That is a defect. So I need to fix my library part. ventosus on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=8#post-26076 Fri, 17 May 2013 16:40:28 +0000 ventosus 26076@http://forums.leaflabs.com/ @gbulmer, most laser cutters have two modes: (1) vector cutting and (2) raster engraving. In cutting mode, the laser cutter acts as a plotter. It takes a vector graphic as input and the laser head moves along those lines, circles, etc, like a plotter. In engraving mode however, the laser cutter acts as a printer. It takes a raster graphic as input and engraves your image line-by-line with a given resolution onto your medium. If the medium is thin enough, you'll just engrave through it... I've been in my FabLab yesterday and tried out the method mentioned in my previous post, and the results were superb. For the bigger apertures, it's fine to use the vector cutting mode (as its much faster). For smaller apertures (e.g. 0.5mm) you want to use the raster engraving mode at the highest resolution. These are the settings I've found to be ideal for an Epilog Legend (60W) for 0.12mm mylar stencils: Raster engraving for the 0.5mm pitch apertures: - Resolution 1200 DPI - Speed 30% - Power 18% gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=8#post-26075 Fri, 17 May 2013 15:32:58 +0000 gbulmer 26075@http://forums.leaflabs.com/ soycamo - "the laser cutter I've used works as a printer, so I've seen good results by setting it to "print" at 1000dpi. You can use old x-ray sheets from dentists' offices. " I am not clear what "print" might mean. Are you using the laser cutter to cut through the material (I'd call that "cutting"), or just exposing "x-ray sheets" without cutting (I'd call that "printing")? If you're only exposing it without cutting, how do you make a stencil with holes? I can use Eagle to generate the stencil, as Gerber's, png, pdf, and dxf. The DRC->Masks dialogue is designed to set the masks parameters (solder resist and via tenting, and solder paste stencil) for direct generation of the appropriate layers, and I do not know a reason to use photoshop. It is a while ago since Chris did the experiments, so I may be wrong. I think we left the DRC->Masks->Cream at their default 0/0/0 values. Making the stencil apertures 70% smaller would be a good thing because it helps retain the 'web' of stencil material between those laser cut holes. gbulmer on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=8#post-26074 Fri, 17 May 2013 15:14:02 +0000 gbulmer 26074@http://forums.leaflabs.com/ siy - Making the solder paste stencil using etching is a good suggestion. However, I am concerned on a few areas: 1. I would prefer to use a technique that is easy for hardware beginners to use without my involvement. I actually think more people have access to laser cutters than to etching equipment (in the UK). I think folks often use pre-coated photoresist which doesn't need developer. AFAIK, dry film photoresist uses a developer. Is that correct? 2. Might using cans as raw material a bit too challenging for schools? I would be worried that folks would cut themselves. Is there a good way to make handling the can easy and safe? Using thin aluminium sheet with a nice rounded edge might be okay. gbulmer on "WM8762 DAC" http://forums.leaflabs.com/topic.php?id=11698#post-26073 Fri, 17 May 2013 14:54:20 +0000 gbulmer 26073@http://forums.leaflabs.com/ pyrohaz - There are a bunch of approaches to improving the audio output. What is driving the choice of 48KHz sample rate? Are you trying to use existing sound sources which require 48KHz? How accurate must the frequency of the sound be? For example, do you have perfect pitch and you could hear small deviation? Are you playing music with other instruments which can't be tuned? One approach to higher quality sound is to use the "Audio Codec Shield": <a href="http://www.openmusiclabs.com/projects/codec-shield/" rel="nofollow">http://www.openmusiclabs.com/projects/codec-shield/</a> "The Audio Codec Shield is an Arduino shield that uses the Wolfson WM8731 codec, capable of sampling and reproducing audio up to 88kHz, 24bit stereo. ... The WM8731 has a lot of useful features, and routines have been written for most of them for both Arduino and Maple" You can buy it online, e.g. <a href="https://www.sparkfun.com/products/11290" rel="nofollow">https://www.sparkfun.com/products/11290</a> Another approach to accurate frequency might be to replace the Maples 8MHz crystal with a 12.288MHz crystal, eg.: <a href="http://www.digikey.com/product-search/en?pv139=30&FV=fff4000d%2Cfff8016d%2Cb8434d&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25" rel="nofollow">http://www.digikey.com/product-search/en?pv139=30&FV=fff4000d%2Cfff8016d%2Cb8434d&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25</a> Then the 6.144MHz can be directly generated by a timer, with no software overhead. mlundinse on "WM8762 DAC" http://forums.leaflabs.com/topic.php?id=11698#post-26072 Fri, 17 May 2013 12:27:36 +0000 mlundinse 26072@http://forums.leaflabs.com/ Hi You can run the chip at 6 MHz, with 128fs that gives 46.875 kHz sampling rate, nonstandard but perfectly ok if you are driving an analog output. Theres nothing special about the 44100 and 48000 samplerates apart from beeing commonly used and makes digital sound connections work better. Another possibility is to run at 125fs, and a sample rate of 48kHz, this is 3 clocks off, not optimal but the chip will tolerate up to 8 cycles deviation from 128fs. A 6MHz timer interrupt will eat all your processor cycles just entering and leaving the interrupt handler. Matching the resistors and using high precision resistors should make a definite improvement in sound quality. Regards Magnus pyrohaz on "WM8762 DAC" http://forums.leaflabs.com/topic.php?id=11698#post-26055 Thu, 16 May 2013 23:08:08 +0000 pyrohaz 26055@http://forums.leaflabs.com/ Hey guys, My synth is going absolutely awesomely! Currently, the audio output is done using two 8bit PWM outputs at ~282.5kHz. I'm writing 16 bits of data at the moment using the small snippet: pwmWrite(2, PWMWriteVar&255); pwmWrite(3, PWMWriteVar>>8); Where pin 2 is connected to a junction through a 56k resistor and pin 3 is connected to the same junction through a 220ohm resistor. While this is a pretty shoddy DAC (as you can imagine, the resistors alone are partially mismatched!), I want to improve the quality. I'm looking at using the WM8762 (<a href="http://pdf1.alldatasheet.com/datasheet-pdf/view/174592/WOLFSON/WM8762GED/RV.html" rel="nofollow">http://pdf1.alldatasheet.com/datasheet-pdf/view/174592/WOLFSON/WM8762GED/RV.html</a>) as its cheap and readily available. My sample rate is 48kHz. Now what i'm wondering is that according to the data sheet, the MCLK needs to be fed a minimum of 128fs, up to 50MHz (I wouldn't be looking for that much oversampling obviously!), now obviously this means I need to generate a clock of 6.144MHz. Is there any way to easily do this on the maple? I know I could probably configure a spare timer to toggle an output but getting exactly 6.144MHz would require a prescaler of 11.71875 which just isn't possible! Would the chip be likely to "complain" at a master clock of 6MHz instead? Also, how much jitter would firing an interrupt every 6MHz and writing to a GPIO cause? If using this DAC wouldn't be a particularly good idea, are there any better ways to create a 16bit output at 48KHz? Would my current PWM method suffice with using precisely matched resistors, such as 300ohm and 76.8kohm? Cheers, Harris soycamo on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=8#post-26054 Thu, 16 May 2013 14:04:30 +0000 soycamo 26054@http://forums.leaflabs.com/ @gbulmer @sly the laser cutter I've used works as a printer, so I've seen good results by setting it to "print" at 1000dpi. You can use old x-ray sheets from dentists' offices. My friend has used parchment paper (!) with okay results. In Eagle you just use the "paste" layer and shrink the pads. I have done this with Photoshop but you can also do it using the design rule check thing. soycamo on "Laser Tag Revolution, showing off a project I worked all semester on!" http://forums.leaflabs.com/topic.php?id=11692#post-26053 Thu, 16 May 2013 14:00:20 +0000 soycamo 26053@http://forums.leaflabs.com/ What's your GitHub handle? bubulindo on "passing a class method pointer as a function pointer" http://forums.leaflabs.com/topic.php?id=11679#post-26047 Thu, 16 May 2013 07:56:46 +0000 bubulindo 26047@http://forums.leaflabs.com/ Yes, that seems to be the solution. I'll leave the revolution counting bit out of the library for now. I should have a working version in two weeks (after my vacation). :) mlundinse on "passing a class method pointer as a function pointer" http://forums.leaflabs.com/topic.php?id=11679#post-26046 Thu, 16 May 2013 06:53:59 +0000 mlundinse 26046@http://forums.leaflabs.com/ Use a global that is set somewhere, you can even let the timer handler switch the current Encoder to the next object of an array of objects: gCurrentEncoder * Encoder; And then let your interrupthandler be: void my_timer_handler() { gCurrentEncoder->timer_interrupt_handler(); /* Determine whitch Encoder object to call next ?? */ } bubulindo on "passing a class method pointer as a function pointer" http://forums.leaflabs.com/topic.php?id=11679#post-26045 Thu, 16 May 2013 06:24:13 +0000 bubulindo 26045@http://forums.leaflabs.com/ Ok... Thanks for the help. Guess the revolution counter will have to be done somewhere else then. :( mlundinse on "passing a class method pointer as a function pointer" http://forums.leaflabs.com/topic.php?id=11679#post-26044 Thu, 16 May 2013 06:10:51 +0000 mlundinse 26044@http://forums.leaflabs.com/ if the C function can call to a memeber, the that call is even less possible from inside the timer interrupt handler. There is no current Encoder object "this" in the interrupt handler context, so your approach doesnt work. Your mtehod must be called like anEncoderObject.timer_interrupt_handler() and there is no way to pass the encoder object instance to the timer interrupt handler. If you have several encoder objects, how should the handler know which to select ? If you only got one then use a C adapter class. The error message simply says that your class method is not possible to use as a C void func void.