I want to use the stock display as a gauge for boost, AFR etc. I think that would be awesome if the digits could say something like -2.0B 11.3AF (just as an example).
I envision using the DISP button to toggle between radio and gauge display, since all it does now is switch between C/F when you hold it down.

What I would do is design a small microcontroller powered module to sit inline, and accept sensor inputs as well. Normally it would just pass all signals from the head unit though, unless in gauge mode. Then it would still let though the signals to change the non-text segments (HVAC mode etc). I am an electrical engineer, so this is totally doable. However I need to know the signaling protocol to the display. I've already tried calling Mazda and Sanyo, and been rejected. Metra has evidently been able to figure it out, seeing as their kit controls the display directly, even with custom text. But they wouldn't divulge the signaling spec either. So to see how feasible this is, I need to know what the connector to the display looks like. Is there just one? How many pins? Does anyone have closeup pictures of it?

 

that would be cool. perhaps an arduino interfacing with metra and/or some type of odb2 dongle?

 

so basically something like this?

 

no i think he's talking about the reddish lcd below the carputer screen

 

I also wanted to do something like this, but I wanted to run a DFT on the audio signals and display the spectrum analyzer output as a bargraph.
However, the display almost certainly has it's own controller that communicates through SPI or I2C or something because there sure aren't enough wires in that little harness to control each pixel individually.
Bad for me, as there probably aren't characters in the built in font to display each possible level for what I wanted.
Good for you, since you're wanting to do plain text and these are well documented protocols.

If it were me, I would crack open the back of the LCD and look for any ICs then search for datasheets. You'll probably only have to tap in to 2 or 3 wires if it's one of the aforementioned protocols. Of course this is all complete speculation and I could obviously be way off

Here's a site I found with some info on the mazda 3 radio bus communication. Unfortunately, there's no info for anything LCD related, but it's still interesting:
http://mazda.davidoshea.homelinux.net/radio/

~Chainu

 

https://www.rx8club.com/series-i-tech-garage-22/my-invention-best-boost-can-gauge-ever-oem-red-lcd-display-195323/

Problem solved!

I can upload custom fonts, so a graphic spectrum is totally doable. Let me know if you ever go through with this, I'll send you the specs on the signaling.

 

I am thinking of venturing into hacking the red led/lcd display. Though I saw your (pieter3d) post about the info on the protocol and signaling somewhere but just couldn't find it anymore when I needed it... Could you please help me out?

Lots of thanks...

 

Looks good very innovative.

 

https://www.rx8club.com/showthread.php?t=195323