[PD] Advice on creating an external object for controlling a DAC breakout board

Alexandros adrcki at gmail.com
Sun Aug 16 11:26:57 CEST 2020

Ok, I scanned through your code and your object doesn't depend on
wiringPi, and it's actually a really nice object. By no means would I be
able to write something as close to this!

I have one question though, in the help patch you write the following
comment: "Only one I2C device is available on the Pi.". How come? Don't
I2C devices all connect to one bus and listen only when they are
addressed? Currently I don't have more than one I2C devices to check,
but only one.


On 16/8/20 10:31 π.μ., Alexandros wrote:
> Actually you're right, signal rate could be an overkill for something
> like that. I'll go with control rate. Does your object use wiringPi? If
> so, I'd go for creating a new object as wiringPi is now deprecated as
> stated here http://wiringpi.com/news/ since the developer got bullied
> about support and all. I'll try the pigpio software. Still, I'll give
> your object a try and peek into the code, thanks!
> Anyway, thanks for the hints!
> Alexandros
> On 15/8/20 10:02 μ.μ., Martin Peach wrote:
>> Hi Alexandros,
>> I made an external  [pii2c] which should be available via deken along
>> with the source code. You could use that to talk to the dacs, but not
>> at signal rate. What you want is already done by any 4-channel USB
>> audio interface for much less hassle, and better resolution with [dac~
>> 1 2 3 4]. The 4-DAC board could be used to provide control voltages
>> for an analog synth or something like that at control rate (once per
>> 64-sample block).
>> Martin
>> On Sat, Aug 15, 2020 at 2:25 AM Alexandros <adrcki at gmail.com> wrote:
>>> I want to create an external object to control a quad DAC board with a Raspberry Pi, namely this one. As the object should run at signal rate, I'm confused as to how I should control the rate of values sent to the DAC.
>>> Since all signal objects in Pd work on DSP ticks, processing as many samples as the block size as fast as possible, how should I go about sending values to the DAC on a one-sample based clock? Is resampling the way to go? If so, how can this be done? I'm checking the source files, specifically d_dac.c and m_pd.h, but can't make much out of it. My C skills are very limited, hence all the questions above...
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