Having issues with the InnoMaker HiFi DAC HAT

[alexras]

I'm having trouble connecting mt32-pi (version 0.11.0, running on a Raspberry Pi 3B+) to an InnoMaker HiFi DAC HAT (https://www.amazon.com/dp/B07D13QWV9?psc=1&ref=ppx_yo2_dt_b_product_details).

I've set i2c_dac_init = pcm51xx and i2c_dac_address = 4d in mt32-pi.cfg, and have verified that the DAC itself works by booting the Pi with Volumio. I've further verified that the DAC's i2c address is 4d with i2cdetect (or, to be precise, the only device that i2cdetect -y 1 detects is at address 4d). I'm unable to get audio out of the DAC via either the 1/8" jack or RCA, but I can get audio out of both the pi's 1/8" jack (via output_device = pwm) and HDMI (via output_device = hdmi).

I suspect that mt32-pi is having trouble initializing the DAC. When I run Volumio (which can successfully detect and play audio from the DAC), there's an LED labeled D2 (which is lit in the picture attached below) that's very dimly lit when the pi first boots and lights up fully once Volumio has finished booting. With both mt32-pi and stock Raspbian, that diode remains dimly lit. I haven't been able to find specific references to that diode in the DAC's manual, but I suspect that's the "I've received the appropriate i2c commands and can play audio now" light.

Judging by the wiki and other discussion posts here, this hardware configuration seems like something that multiple people have gotten working before, so I'm kind of surprised it's not working for me. If anyone has any advice for how to proceed with debugging this, I'd really appreciate it.

[dwhinham]

Thanks for testing this DAC.

This is going to be very similar to #194 - mt32-pi needs some extra stuff to handle the more up-market DACs that use their own clocks (act as master devices) rather than the Raspberry Pi's clock (acting as a slave). I can see that this DAC is similar to the Allo Boss in design and uses the same driver.

I have a new HiFiBerry DAC2 HD sitting on my desk waiting to be tested, so getting that working will probably get your Innomaker working too.

I'll need some time to investigate this but now that v0.11.0 is released it's next on my to-do list.

Cheers 🙂

EDIT:

I see that this was reported as working in the Wiki; unfortunately I have no way of verifying this as I don't own this DAC, so I'm not actually sure how many other people have tried it. It's possible that some kind of board revision broke things.

I can also see the driver uses a GPIO pin to (un)mute the DAC (maybe that's also what your LED indicates?).

The mute control is on GPIO 6 (physical pin 31). You could try pulling this up to +3.3V to unmute the DAC (e.g. a jumper wire between physical pin 1 and pin 31). This would normally be the driver's job.

DISCLAIMER: Not my fault if something breaks!

Finally, try different sample rates; 48000 is the default, but 44100 might make a difference.

[dwhinham]

The collisions with hd44780_4bit will only apply if you actually enable hd44780_4bit - are you using this driver? I was actually thinking of deprecating this driver as I currently have no way to test it any more.

If you are using a more common/convenient I2C-based display then this should not affect the DAC.

[alexras]

Turns out I am! I bought one of the older HD44780s because they were a few dollars cheaper. Uhh, whoops! Rookie mistake I suppose.

I'll order an i2c-based display. If I end up getting this to work by just disconnecting the display, I'll edit the wiki to reflect the fact that there's a mutual incompatibility there.

[dwhinham]

Thankyou, that would be helpful.

I haven't fully committed to deprecating the hd44780_4bit driver, it's just that I have no idea whether it is still working or not - although I haven't received any complaints lately so maybe it's fine. 🙂

If you wanted to use your current screen, you could add an I2C backpack to it, something like this: https://www.amazon.co.uk/GeeekPi-LCD1602-Adapter-Interface-Expansion/dp/B088M5YFJP/ref=sr_1_3?keywords=i2c+adapter&qid=1639514092&sr=8-3

Many of the "I2C HD44780" screens are just regular HD44780 screens with one of these attached.

[alexras]

It appears that the collision between the hd44780_4bit driver and the DAC is to blame. Set the display to none and sound plays just fine without pulling up GPIO#6, although that D2 LED doesn't light up brightly like it does with Volumio.

I also had to set the sampling rate to 44100 to correct some sampling artifacts. I'll make a note of both of those in the wiki.

[dwhinham]

Great, thanks for this!

It should be possible to use this DAC with the higher sample rates just fine, but I will need to add support for putting it into "master" mode and telling the DAC which sample rate to clock at, as mentioned in my first reply. My guess is that it starts up in a mode that expects 44100Hz, but the default mt32-pi mode of 48000Hz is mismatched; the driver will need to poke the DAC and get it to switch properly.

It would be worth re-testing once I do that because that is how this DAC is really supposed to be used.

[rsn8887]

I have the same DAC and Raspberry Pi 3B+ but a different display and it all works for me. The LED you mention lights up when I power on my Rpi. I use the same config as you, but I also added usbpowerdelay=2000 to my cmdline.txt as described here: https://github.com/dwhinham/mt32-pi/wiki/USB-MIDI-interfaces , because I am using an ESI Midimate EX USB Midi interface. The display I use is one of the big green ones that work with the hd44780_i2c driver (Low-Cost 2002 20x2 Charcter LCD Module Display Yellow Black Color, VDD=5.0V, I2C Adaptor Board with Dupont Wire for Arduino from BuyDisplay.com)

[alexras]

Thanks! Turns out relying on 4-pin rather than i2c was the issue here.