Oh oh, my newly modded radio has no display output

[tilmanb]

I just finished my new radio. In true hacker fashion I took it apart straight out of the box. I never even bothered to check if it worked before I modded it.
I guess I should have. Because now I'm not getting any display output. The display is ok, I tested with a known good one and that also did not work.

I did the programmer mod and FrSky telemetry mod.
The programmer worked. I was able to read and write the firmware.
The FrSky mod is so far only moving those buttons over to the other pin with the resistors. The TX and RX ports are as of yet unconnected. (Missing the TTL level converter still)
I unsoldered the FrSky mod cables because they are the only mod that is kind of hit and miss with those little pins on the MCU.

I think the radio works fine otherwise. It beeps when I switch it on.

Any idea what I could have busted? Any easy things to test?
I had all the peripheral boards off and put them back in. But I can't see much going wrong here.

I have a oscilloscope and multimeter to do testing...

[Kilrah]

Hmm, a good place to start would be to check all MCU pins and the LCD connector are properly soldered. Check the LCD voltage supply too.

[jhsa]

Is the radio that beeps, or is it the frsky module beeping? also does it move servos when you connect a receiver?

[tilmanb]

Ok, it can't be completely dead. I'm measuring PPM pulses on the PPM output and I get 'data' on all (most) of those test points in between that row of resistors.
I measure 3.3v on pin 2 of the LCD connector. The first pin (left) seems unconnected.
However, I measure no signal on any side of those capacitors(?) directly under the display port.

I had lifted one o those pins where the buttons got moved with my wire. But that was when I de-soldered it to check the joint and I got it soldered back on.
Apart from that I can see no issues with the soldering. Especially not towards the LCD port.

[tilmanb]

I did not test with a radio module connected. But I guess the fact that I got PPM pulses after I acknowledged the switch error beep says it all.

[jhsa]

ahh ok.. If you have PPM then the radio must be working. Try applying gentle pressure on the CPU, there were cases of unsoldered pins lately.. Also make sure the LCD ribbon is seated properly and the LCD connector is locked.

[tilmanb]

The soldering of the CPU looks spotless. Also tried pressure.
Also the soldering of the display port. And I verified with my mates radio that the position of the display port is correct and that I also see no signals on the display port pins. (have to figure out what I do wrong there with my oscilloscope)
It's really weird because the none of the display stuff is in any way directly related to my other mods. I mean really, I just touched the SPI pins on that board and the frsky pin swap. The display stuff is on different ports.

One pretty stupid idea. Could it be that the display comes up with zero contrast? I suppose there is a analog pin for that, does anyone know which?

[Flaps 30]

Assuming the firmware you loaded onto your TX was/is Er9x. You could read back from the radio the information regarding the general settings. In setup you will find the contrast setting. I use a setting of 26 and that gives a reasonable contrast.

[tilmanb]

it's open9x

[kaos]

That happened to me just like you described, only I had a blank lighted screen, it turns out it is the stupid LCD ribbon is not fully seated. that thing rocks like a boat if not seated with both ends together.

[Flaps 30]

it's open9x

Same applies.

[tilmanb]

If I had the schematics I could perhaps better understand where and how to trace the signals and probe for connectivity. I'm pretty sure all the solder points and connectors are well seated, it must be more subtle.
I will also try to read the contrast setting from eprom. But now I'm stuck at work first. :/

[Rob Thomson]

This help?

viewtopic.php?f=44&t=199

[tilmanb]

Thanks. That is actually very helpful. Also for other stuff I'm working on.