[MTCD  Android Head Units Q&A] forbiddenera:
Hi,

I run a car audio firm, we have a PX5-based unit a client ordered.. The MCU version is "MTCD_WWW_V2.54b_2" .. Our goal is USB audio working proper, among a few other things (better interface if possible, better apps, better SQ stuff)

I haven't seen a "www" mcu anywhere? It's sold as an EONON GA7150A..

Anyone know anything about this MCU? If it's compatible with any others or anything like that? I definitely would like to root it, update the ROM to something better, get rid of the "Windows Mobile" part of it which was, IIRC, advertised as the ability to 'boot' between Android and Windows but is actually just a different interface theme from the home screen.. Also want to do whatever we can for sound quality and smooth experience.

I should note that, as a car audio company (in Canada), we are seriously considering producing our own Android units.. likely 'producing' would consist of getting units like a px5, branding them and primarily, having a SOLID software system built for automotive use. I think a lot of these units are a great start and are ALMOST there for a lot of things but..some of the interface stuff is rushed, not translated great, etc.

What I'd like to see is an Android unit, priced like these ones usually are, but with *really* good class A interfaces. The kind of experience you'd expect on a Samsung phone or a Pioneer headunit. I personally have been using my Samsung Tab S 8.4" in my car as my 'head unit' (paired with a Pioneer single din for a hardware volume knob and some easy control) for along time and I would not want to ever go back.

Here's a short video of the interface and version info..

[YOUTUBE]apSq38hV2Fw[/YOUTUBE]

My eventual goal is getting USB audio working decently. It does work for most Android apps but the volume control only controls the internal audio chip, and the radio app routes through the internal audio chip as well.. I assume perhaps other sources like DVD and line-in would as well, I haven't verified but I will pretty quick here. I plan on making another video showing what works/what doesn't/how it works.

I'm hoping for a software only solution but am happy to hack the hardware if needed. I'm using a Behringer UCA-222 as a "DAC" (same as 202 but red in color) but won't actually be using the DAC in it but only it's optical output into an Audison Bit 8.9 DSP/Amplifier.

There's the possibility of routing the px5's audio output RCA's to the Behringer's Input and 'monitoring' that input to the optical output via software but that doesn't solve the fact the volume control does nothing for apps when using the USB.. Eg, youtube plays through USB/optical fine but volume control doesn't change the volume..Radio plays through the px5's audio chip and volume control controls that, and shows on screen.. I could force everything to play thru the px5 audio chip and then monitor it to optical but that defeats the purpose of what I'm trying to do completely (full digital audio to the amplifier).

I'm willing to sacrifice some sources re-routed like that though, eg, the radio would be fine as it already sounds ****. Aux in also doesn't sound great usually and won't be used in this car anyway. DVD would be nice to have optical out as well but

I'm currently still searching for a schematic/block diagram for these devices, this would probably answer a lot of my questions like.. I'm curious whether audio from any of the other onboard devices (radio, dvd, aux in) go through Android at all or whether they're directly sourced to the output chip.

If it's the latter - that sucks - but I wouldn't be surprised. I have read the thread about the hardware hack to allow android control of the audio chip but I don't see this giving me the functionality I need. If it is wired like this, and I can get the other components (eg. radio chip) to output their audio to Android, digitally somehow and have Android push it to the USB audio device that'd be cool.

Is no one else using a USB dac on any of these units? I have many years experience coding, hacking, electronic engineering, tinkering, etc. including Android but I haven't done many of these Android Head Units.. A lot of times we use tablets instead! But this client wanted OEM look..so we thought we'd give it a shot.

The difference between the audio quality from the internal DAC and the USB audio device's optical routed directly to the DSP (digital to the power amp) is definitely noticeable, even with there being very little noise picked up in our interconnects.