I wrapped up the radio for the time being.  It’s not internally 100% the way I’d like it but I need some time to work with it before I consider the firmware truly final.

A few notes:
1)  I traced out the radio LCD backlight wiring.  There are four LEDs in series with the high side connected to 10 volts and the low going through a transistor and resistor.  I had previously found that 1k in series was nice for general LCD lighting and full 5 volts for high brightness.  I tied the new display positive backlight to +5 and the negative to the collector of that transistor.  I put a 1k resistor across the transistor and shorted out the 220 ohm resistor.  Here is what that mod looks like:

Yes, that’s a really tiny resistor I used!

2) The flex cable to the front processor board is not very robust.  Earlier I lost the ability to turn the radio on and found that the pin 40 to pin 40 connection was lost in the cable.  Now the 3 bars started going intermittent and I traced it to the loss of connection in pin 39.  Here is my fix:

About the only choice seeing as the part is unobtainium.  But it works great.

3)  The new LCD display annoyingly requires a negative ~1.66 volts for bias to work.  More annoyingly there is no negative supply I could find in the radio so I had to make a small 555 based charge pump.  I would prefer to use a tiny SO-8 part to do this, one meant for the purpose, but that will have to wait until I have enough to order from Digikey to have a reasonable size order.  In the meanwhile I stuffed it here:

Left of that are three precision resistors which make the voltage divider for the voltage display I added.  When I go back in I will tack glue three SM resistors on the other side to eliminate this eyesore.  Here is where the sense wire ends up connecting to the CPU board pin 39:

I didn’t take a photo of it but have the 6 wires from the Arduino going to a tiny connector which is between the boards.  I can connect my code development computer to it if I want to update the code without having to disassemble the whole thing.

I took a video but it is too large for this site so I placed it on my site at the following address:

http://petergottlieb.com/images/syncal.mov

Note that when the display goes to the bright setting the iPhone camera can’t handle it and washes out.  It’s pretty bright, gotta love these new high efficiency LEDs!

Now I play in the field!