Repurpose seed pins

[dimduj]

Hi everyone,

I’ve a project in mind and I will need more dac and adc (cv) than the seed actually offer.

Is there a way to repurpose some pin ( sai pins for example ) into pwm ( for output sub audio cv modulation) or adc (for potentiometer analog read) ?

If not possible, how would you handle this ?
Switch Multiplexing, external adc dac or considering another board ?

Thanks for any advice

Dimitri

[MikeDB]

Yes the STM32H750 is full of all sorts of useful alternative functions on the pins, including loads of timers. Best to download the datasheet and the Seed circuit diagram from Github so you can work out what’s available.

[shensley]

Many of the channels support PWM output (and the ones that don’t could be configured to do so in software). Currently this isn’t built-in to libdaisy, but the arduino integration will automatically configure hardware or software PWM for any of the daisy pins. Using an external DAC via SPI is also an option, and depending on your requirements would probably be my recommendation.

As for analog inputs, the Daisy Seed has 12 inputs capable of being ADCs. If you need more than that (as often is the case) you can use a multiplexor like the CD4051 to send multiple inputs to a single pin. The code for this is built into libdaisy, and you can use the Daisy Field Schematic, and initialization code reference for doing something similar yourself.

[dimduj]

Thx for the answer and the references in the code

If you don’t mind, I’ve a lots of question regarding your previous answer , but I will not be offended if you haven’t the time to answer them…
I need to do some homework here

What would be the maximum number of ADC that i can configure on the daisy seed (if i sacrifice some other function) ?
What would be the maximum number of PWM that i can configure on the daisy seed (if i sacrifice some other function) ?

I usually see multiplexed pot ADC reading (like in the field and on Mutable Intstrument elements for example) but I rarely see this kind of multiplexing on CV.
Is there a reason why ?
What kind of refresh rate can I expect ? will this multiplexing result in laggy UI or it is so fast that It is transparent ?

Is there any penalty to use an external adc instead of the built in adc ?

Last question do you have recommendation about ADC/DAC chips ?
What are the specs I need to pay attention (except resolution, # channels and price).
SPI or I2C ? (I think SPI is faster, until 100Mhz ? Do i need that speed )
I would tend to choose 12 to 14 bit resolution and 8 channels but i guess there is other things to check.

A possible plan is to use the DAC8168 ( 16 bit 8 Channel used in mutable stages)… MAX11131 could also be a good candidate for thé adc side

Notes/references :

Multiple multiplexer (4051) sharing the same address, but diferent analog input pin

Hello, I’m still learning the software and hardware aspect around the daisy. Sorry if it’s an obvious question, but I did not find example of hardware using multiple 4051 mux. Is it possible to have multiple multiplexer sharing the same 3 pin for the address, and connect the output to different analog input pin? for the board definition initialisation, will something like this works ? // POT MUX adc_cfg[0].InitMux(seed.GetPin(PIN_ADC_POT_MUX1), 8, seed.GetPin(PIN_MUX_SEL_0), seed.GetPin(…

https://www.st.com/resource/en/application_note/dm00628458-getting-started-with-the-stm32h7-series-mcu-16bit-adc-stmicroelectronics.pdf

[justin23000]

@dimduj

Last question do you have recommendation about ADC/DAC chips ?
What are the specs I need to pay attention (except resolution, # channels and price).
SPI or I2C ? (I think SPI is faster, until 100Mhz ? Do i need that speed )
I would tend to choose 12 to 14 bit resolution and 8 channels but i guess there is other things to check.

Just a gentle bump to see if anyone has any input on this? Especially for adding DAC chippies to the seed?