LeafLabs Garden

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1. 

   tlgosser
   Member

   Wow! That's a lot of DSP. Is this a mega-stompbox?

   That is very interesting about a higher frequency data stream causing less noise.

   I use 12bit AD5340s for industrial purposes. It can be latched open so that whatever number you write to the port register comes out as a voltage. Doesn't get any faster than that. That resolution may not suit your needs but since as you say there are no 'complete' registers available that may be the best that can be done. They're $5.16 at Arrow.

   The AD9833 is what I was thinking of for the waveform, also probably unsuitable for audio since they take 6 cycles to change frequency. They do make a clean sine.

   Obviously I am not an audio guy so I will recluse myself. Sounds like an interesting project.

   Posted 2 years ago #
2. 

   pyrohaz
   Member

   I agree with you on that one gbulmer, the data bit rate isn't extremely large. I also completely agree with you on the audio quality, i'm happy with my Cambridge Audio hi-fi, AKG Headphones and Tascam D/A, even with my young ears, I can't hear the difference between a 192kbps MP3 and a standard old Wav file, as much as i'm sure being an audiophile is good, I just don't seem to have good enough ears! I enjoy the music I listen to anyway so thats no worry. Great article though :)

   As you probably know from one of my many last posts, i'm currently using two 8 bit PWM outputs summed together with a 1:256 resistor value ratio to produce the output, while this suffices for the current version of the project, its pretty noisy! And I can imagine that the phase difference between each PWM isn't amazing, not forgetting resistor precision.

   Surprisingly, the TDA1543 has dedicated DACS internally as opposed to any delta sigma stuff, though it is from the very early 90's, probably why its so cheap!

   Do you know if LeafLabs are going to be making any more of the maple series or have they decided to no longer bother? I've recently bought a PIC32MX440 which has a higher DMIPS than the ARM at cost of higher power etc. I've also got the ST discovery STM32F0 board (it was only £7 so I thought why not!)

   And close! Its just a synthesizer project, i'm quite happy to have squeezed all the DSP processing into about 15us!

   It was a good idea to use a stand alone waveform generator, it just unfortunately doesn't suit my needs!

   I was considering using the AD1851 but it required a split supply which I unfortunately don't have!

   Posted 2 years ago #
3. 

   mlundinse
   Member

   For a synth project like this I think the STM32F4Discovery is good.
   Its got an onboard codec and you can pick it up for 17 €,
   Since its a STM32F4 chip it doesnt work well with the current Maple IDE
   but you can use libmaple and download firmware using the USB ROM
   dfu bootloader and an up to date dfu-util.
   You dont have to spend your life bitbanging relucant spi ports,
   an interesting hobby if you like that sort of stuff,
   but a waste of time if you primarily wants to make sound.

   Just my take. I love the Maple and the dev environment
   but its slowly slipping behing the main stream.

   Magnus

   Posted 2 years ago #
4. 

   pyrohaz
   Member

   See I did consider getting the STM32F4 series but the board was massive! Can is be as easily programmed as the maple? I'm fine with low level GPIO changing but i'm not too sure on how to change timers and more complex topics like that, is it hard to move from maple environment to another ARM board?

   Posted 2 years ago #
5. 

   gbulmer
   Moderator

   pyrohaz - "Do you know if LeafLabs are going to be making any more of the maple series or have they decided to no longer bother?"

   LeafLabs staff have posted that they will continue to sell existing Maple designs, but are unlikely to develop a new board this year. A bunch of us are working on newer boards, but right now, these are DIY assembly, which might not be suitable for you.
   The designs are discussed on:
   http://forums.leaflabs.com/topic.php?id=10410&page=10

   and the designs are at:
   https://github.com/gbulmer/openstm32hw

   ventosus has made an STM32F303 board using:
   https://github.com/gbulmer/openstm32hw/tree/master/Orone-mini-v0/Orone-mini-S8A-v0r001

   I've updated that design to use lower-cost components (about 10 GBP + PCB), and hopefully easier to use a 'raw' STM32F303 at
   https://github.com/gbulmer/openstm32hw/tree/master/Orone-mini-v0/Orone-mini-S8E-v0r001

   Posted 2 years ago #
6. 

   gbulmer
   Moderator

   tlgosser - "That is very interesting about a higher frequency data stream causing less noise."

   Sorry if I wasn't clear. Higher frequency sampling might cause more noise. However, if the noise is at a high frequency, it is much easier to filter out, without introducing other signal distortion, than filtering noise near to the audio frequency range. Further, if it is random noise, rather than a repetitive signal, the noise energy is 'spread' across the frequency spectrum and becomes less noticeable too.

   Posted 2 years ago #
7. 

   pyrohaz
   Member

   I like the look of the Orone mini, I'll be looking to definitely make one of them in the future!

   Back to the point of SPI, i've decided to use a much newer DAC that uses straight SPI, its the DAC8411 (I got some free sample off TI since i'm a student luckily!), it can be found:

   http://www.ti.com/product/dac8411

   This chip solely uses SCK and MOSI with a sync line and as far as I can decipher of the datasheet, sync is low triggered so I can just use the standard NSS pin to pull this up once data is finished transferring. The chip does have a 24bit shift register input where the topmost bits determine which mode the chip is in (00 is normal mode) therefore, for this, I can just pulse the data clock twice for these two then initiate serial transfer, after that, it needs an extra 6 "padding" bits which it doesn't care about, the sync is then bought high etc. Luckily, it works at up to 50MHz SPI so i'll be able to use it with full speed SPI.

   I'll update once I receiver the chip!

   Posted 2 years ago #

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