LeafLabs Garden » Forum: Maple Hardware Support

LeafLabs Garden » Forum: Maple Hardware Support - Recent Posts http://forums.leaflabs.com/forum.php?id=3 A place to share, learn, and grow... en-US Sun, 19 May 2013 13:43:41 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://forums.leaflabs.com/search.php 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. "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. siy on "Community rework of standard maple and maple mini." http://forums.leaflabs.com/topic.php?id=10410&page=8#post-26007 Tue, 14 May 2013 10:24:29 +0000 siy 26007@http://forums.leaflabs.com/ @gbulmer, there is a way to create stencils from aluminium cans (a lot of beverages are sold in such cans). It requires established dry film photoresist process and there is a little trick to make foil cut from can flat, but otherwise process is very simple and straighforward. And quite fast, because even in ferric chloride etching aliminium takes much less time than copper. Thickness of the resulting stencil is about 0.15mm which is good enough for most cases. gbulmer on "2 byte data type" http://forums.leaflabs.com/topic.php?id=11575#post-25960 Mon, 13 May 2013 08:12:24 +0000 gbulmer 25960@http://forums.leaflabs.com/ pyrohaz - It might be worth noting for future reference that you could get the compiler to help. <pre><code>void loop() { struct { char a, b; } twochar; // print the size of each type: SerialUSB.print("sizeof(int) "); SerialUSB.println(sizeof(int)); SerialUSB.print("sizeof(char) "); SerialUSB.println(sizeof(char)); SerialUSB.print("sizeof(long) "); SerialUSB.println(sizeof(long)); SerialUSB.print("sizeof(long long) "); SerialUSB.println(sizeof(long long)); // ! SerialUSB.print("sizeof(short) "); SerialUSB.println(sizeof(short)); SerialUSB.print("sizeof(float) "); SerialUSB.println(sizeof(float)); SerialUSB.print("sizeof(double) "); SerialUSB.println(sizeof(double)); SerialUSB.print("sizeof(twochar) "); SerialUSB.println(sizeof(twochar)); }</code></pre>