I am interested in using the daisy for a eurorack module but my application requires the module to be able to sample audio as well as dc signals accurately from the same input. I know most codecs have high pass filters on the input to get rid of any dc component of the signal. The problem is that my idea for a module needs to work the same whether the input is static or an audio signal. Certain codecs allow you to disable this high pass filter so you can sample slow moving sources. I was wondering what the model number is of the codec on the daisy so I can look at it’s datasheet. Or if you know whether it is possible to disable to high pass filter on the daisy.
The codec is an AKM AK4556. The internal high pass filter can be disabled but only physically, by setting one of its pin to high. Moreover, the Daisy has capacitors on the input and output for an additional cancellation of the DC offset.
Could I remove these capacitors/short them and get DC input and output capability? I emailed a bit with OS from expert sleepers, Whose disting and ES-8 have dc coupled inputs, and he suggested using a codec whose high pass filter could be disabled and then trimming any DC component out either in hardware with a trim pot, or in software. Is this something that would be possible with the daisy or do I need to make my own solution?
You’d have to desolder codec pin and connect it from ground to VDD to have DC coupled audio. I think it’s one of the 2 major flaws that current version of Daisy has.
That is frustrating for eurorack uses. Guess I will have to figure out my own solution.
Could you split the incoming signal and route it to both an audio input and an ADC? That way you could decide in software whether you have DC or audio signal to sample, perhaps with an envelope follower on the audio part?
That seems like a bit of a hacky way to do it. I think I’ll just end up making my own board to do it.
Well just an idea, not sure why it’s hacky? Desoldering or shorting AC coupling caps is hacky. And making your own Daisy compatible board sounds like an order of magnitude more difficult!
An maybe simpler aproach could be, to use the second I2S line on the Daisy, to add an Codec in DC Coupled configuration. Still not trivial especially on the driver, but seems in my limited understanding much more doable and is in my interpretation, what the Dude from ES had in mind.
Coding your own driver, could be also avoided, by using the AK4556, which is unfortunately hard to get, since the Fire at AKM.
Now that Daisy has switched codec to the PCM3060, the high-pass on the audio inputs could be configured in software? @Takumi_Ogata is this a setting that could be changed when flashing? Communicating with the codec at this level is a bit beyond my skills.
No, the Daisy Seed has no I2C connection from the STM32 to the pcm3060. The configuration cannot be changed in firmware.