So, I just saw that as a suggestion in other post and I thought it might be cool. I mean, I don't even have my reader yet and I'm super excited about ripping it apart hahah.
Anyways, I was thinking about a couple of things that could be done in order to have sound in the Kobo.
This is the datasheet for the Clara processor:
https://www.nxp.com/docs/en/data-sheet/IMX6SLLCEC.pdf
There are four options I can think of, three of them are absolutely restricted by how exposed are the pins of the IC in the PCB.
1. Using the PWM outputs of the proc to make sound. I'm kind of assuming that the PWM is already used by the backlight controller, I'm not sure about it, but anyways PWM (unless it's really high freq) will not have a decent output quality.
2. Using the Bluetooth interface of the IC: This is doable, but I'm pretty sure that we'll need to add another IC and a custom board. I think this is the hardest option.
3. Using the I2S output and a DAC. There's an I2S interface already available in the proc, and if it's accessible, it shouldn't be *too* hard to be able to hook up a decent digital-analog converter to it, provided we can find the appropriate kernel driver.
4. Stream it through WiFi to another device. This is the most feasible, and
it doesn't need to be your phone. With KoboX, we could create a fake output device and stream it over WiFi to another device. That device can be an ESP8266 with an I2S DAC and a 3.5mm jack. It would not involve modding the device (at least in an electronics level), and the receiver wouldn't be expensive or bulky. The cool part is that it's still WiFi, you can leave the reader somewhere else and, provided there's an access point, listen to whatever thing you have there. The quality should be pretty good, and this would open a lot of new possibilities.
Personally I'd love to see option 2 or 3 working, I mean, it would be reeaally cool. But the streaming option doesn't sound (pun intended) too bad either.
Anyways, this couple of weeks I'm going to be pretty busy but I'm willing to put some time on it.
Any suggestions? Anyone willing to dive into this rabbit hole with me?