Trouble Shooting Eggfinder LCD Build

[TXWalker]

I just finished building the Eggfinder LCD. Everything seemed to be ok until I tried to power the unit up. All I get is solid black squares across the LCD display, no beeps from the buzzer either. I went back and touched up all the solder joints thinking I might have a bad connection. Still no signs of life. I even hooked up the data cable to the USB port on my PC. I can see “prolific” on COM3 is active.

Any suggestions what to try next?

Thanks, Pete

 

[rockladen]

You need to adjust the contrast. It's marked on the board, and it's that little white round dial. Adjust it with a small flat head driver. Mine's was like that and took me a couple days to figure it out.

 

[TBob]

I had this same issue with a fresh one earlier this year. I contacted Cris and he suggested reflashing the software. It does take a data cable to do this. Worked like a champ. I'll see if I can find the procedures.

 

[cerving]

The procedure and the software are on the Eggtimer Rocketry Eggfinder LCD support page... https://eggtimerrocketry.com/eggfinder-lcd-receiver-support/

 

[TXWalker]

Cris, That didn't work. I have not been able to communicate with the device to update the firmware.

 

[tOD]

Cris, That didn't work. I have not been able to communicate with the device to update the firmware.

Did you try the suggested contrast adjustment? I had to do it with mine.

 

[g.pitts]

Cris, That didn't work. I have not been able to communicate with the device to update the firmware.

Do you have a voltmeter? If so, measure your input voltage by putting your red (+) probe on the + PCB pad and your black (-) probe on the - PCB pad. What do you read for that voltage? Then do the same with 5V and 3.3V and let us know what you see for each of the two voltage rails. They should be within 5 percent or so of their expected values.

 

[cerving]

Check your solder joints on the regulators... they look pretty thin from the pictures.

 

[Voyager1]

Is the RF module on the LCD unit flashing in response to an Eggfinder TX unit? This probably won’t help you with the current issue, but it will indicate something is working.

 

[Voyager1]

Check the solder joints around the 10k resistor that is adjacent pins 3 and 4 of the processor. I’m not sure, but it appears that the outer lead might have a solder bridge to the board. If so, that might be holding the processor in reset. It could just be an untrimmed length of lead - it’s a little hard to tell in the image.

 

[Voyager1]

There might be a couple of other spots to check as well. Probably nothing, but in the image they look a little sus in the available lighting and slightly blurred image when zoomed in. I'm probably just seeing bent untrimmed leads and shadows. Double check all solder joints for potential bridges. Also, the solder joints along the RF module, are they OK?

It appears that the processor is not communicating with the LCD module judging by the single line of dark character blocks. In fact, the processor doesn't appear to be booting up at all!

Have you adjusted the LCD contrast as suggested above? Are there any other symptoms that you have noticed? As suggested above by the others, if you have a multimeter check all the voltages from the 3.3V and 5V regulators and trace them around the board.

Also, again if you have a multimeter, with the power off, check across the resistors for correct values and no shorts. Then, when powered up, check the voltage on pin 1 of the processor - I believe it's the RESET pin and it should be high, not at 0V.

 

[TXWalker]

Thanks guys for the advice. I've gone over the solder joints with a magnifying glass and don't see any bad solder joints. The dark joints Voyager is highlighting have a little flux residue. It cleaned off with IPA. I played with the LCD contrast, it goes from all black to all clear as I adjust the contrast. No signs of life on the processor of other modules. I agree the processor is not booting.

I know when I'm in over my head. I packaged up everything and sent it to Connor McGrath to look at.

Thanks, Pete

 

[TXWalker]

I thought I should give a final update on my Eggfinder LCD build. I was unable to get the unit to wake up after assembly so I shipped it to Connor McGrath to see if he could figure out what was wrong. He said he could not get it working either. All the solder joints looked OK but the main processor was not working. Connor shipped it back to the factory and sure enough the processor was bad. Eggtimer replaced the kit and I had Conner assemble the new kit. Today I was able to finish the assembly and try the receiver out with the TX unit I had built previously. Hurray! Everything is working perfectly. I had five satellites and "found" the TX unit in the back yard. I can't wait to try it out in a rocket!

I'd like to give a big shout-out to Connor for all his help diagnosing the issue. Also to Eggtimer for replacing the unit no questions asked.

 

[Idunno]

I thought I should give a final update on my Eggfinder LCD build. I was unable to get the unit to wake up after assembly so I shipped it to Connor McGrath to see if he could figure out what was wrong. He said he could not get it working either. All the solder joints looked OK but the main processor was not working. Connor shipped it back to the factory and sure enough the processor was bad. Eggtimer replaced the kit and I had Conner assemble the new kit. Today I was able to finish the assembly and try the receiver out with the TX unit I had built previously. Hurray! Everything is working perfectly. I had five satellites and "found" the TX unit in the back yard. I can't wait to try it out in a rocket!

I'd like to give a big shout-out to Connor for all his help diagnosing the issue. Also to Eggtimer for replacing the unit no questions asked.

I have a problem similar to this one. Was there a bad batch of processors sent out during the summer? Mine shipped early July but just got around to soldering it. The LCD comes on, I get a long beep, but the screen is blank. Pin 1 is 0V, is that supposed to be 3.3V? Resistors all seem to be in just fine, capacitors are the correct polarity and the 3.3 and 5V regulators seem to be working.

 

[Voyager1]

If you're referring to Pin 1 of the processor, that's the RESET pin. If it's at 0V, then it's being pulled low by a solder bridge or reset button, if installed. Check your solder joints around the 10k resistor that's adjacent pins 3 and 4, making sure the leads aren't shorting to the PCB GND plane; and check the RST pads on the corner edge of the PCB.

 

[cerving]

Not aware of any bad processors... the one that was in the OP's kit may have not been flashed properly. If you get a beep, the processor is working... did you adjust the contrast?

 

[Idunno]

Not aware of any bad processors... the one that was in the OP's kit may have not been flashed properly. If you get a beep, the processor is working... did you adjust the contrast?

Yeah it's just like the OP's picture submitted. If I turn the contrast all the way up I get one blank line and one solid line. Adjusted down and the screen is blank. Would a picture be of use? I guess flashing would be the next step?

 

[Idunno]

If you're referring to Pin 1 of the processor, that's the RESET pin. If it's at 0V, then it's being pulled low by a solder bridge or reset button, if installed. Check your solder joints around the 10k resistor that's adjacent pins 3 and 4, making sure the leads aren't shorting to the PCB GND plane; and check the RST pads on the corner edge of the PCB.

I measured about 0.2V on that pad, must be a short somewhere. I'll snoop around, thanks for the tip.

 

[Idunno]

I measured about 0.2V on that pad, must be a short somewhere. I'll snoop around, thanks for the tip.

Turns out I had power and ground backwards when I took that last measurement. I'm getting 3.2V on pin 1. Any other ideas?

 

[cerving]

Check the solder joints on the header and socket for your LCD panel. You may have a bad LCD panel, too... we've had a few of them.

 

[Voyager1]

Turns out I had power and ground backwards when I took that last measurement. I'm getting 3.2V on pin 1. Any other ideas?

Are you saying that you had the battery connections reversed?

 

[Idunno]

Are you saying that you had the battery connections reversed?

No no, i'm saying I had the + and - leads on my volt meter reversed.

 

[Voyager1]

No no, i'm saying I had the + and - leads on my volt meter reversed.

OK. If you're getting a solid line and a blank line on the LCD, that suggests that the processor is not communicating with the LCD module. There are two possible (at least) reasons for this:

1. Your processor is not booting up, or is dead. Since you do hear a long beep when you power it up, then this is probably not the case. It is booting up and initialising.
2. Your LCD module is faulty, or the connection to the LCD is faulty. This is more likely the case.

As Cris suggested, check the header connections to the LCD.

Good luck.

 

[Idunno]

OK. If you're getting a solid line and a blank line on the LCD, that suggests that the processor is not communicating with the LCD module. There are two possible (at least) reasons for this:

1. Your processor is not booting up, or is dead. Since you do hear a long beep when you power it up, then this is probably not the case. It is booting up and initialising.
2. Your LCD module is faulty, or the connection to the LCD is faulty. This is more likely the case.

As Cris suggested, check the header connections to the LCD.

Good luck.

I'll do some more checking tomorrow, but as far as I can tell everything is okay. Are there maybe some specific pins that are more likely than others? I do believe the processor is booting up, because it there will be some blocks, then they will go away then they come back. I think this is the processor attempting to show some different text.
I have inspected all of the pins and pads and added more solder. I did a continuity check from top of the LCD to bottom of the PCB and everything checked out. I also did a continuity check between adjacent pins to verify there were no shorts. I guess I can get ohm readings to see the resistance values are as expected.

 

[Voyager1]

What happens if you back off the LCD contrast? Do you see any characters, instead of blocks?

 

[tsmmiller]

I have the same issue, and the LCD looks exactly the same.
Comunicating with Cris I exchanged both voltage regulators and the capacitors. Still had the same issue.
I never did hear a beep on mine, and just tried to adjust the contrast.
No luck on mine.
I chalked it up to beginners error and will order a replacement for round two shortly.
My TRX however seems to function as designed!

 

[Idunno]

What happens if you back off the LCD contrast? Do you see any characters, instead of blocks?

If I back off contrast I see nothing. But this is a 2 line lcd screen right? Why would I only get one line showing with contrast all the way up. Strange. I'm going to attempt a reflash. If that works maybe i can just try another display.

 

[cerving]

Since it's beeping, you probably have a bad LCD display. Email us and we'll get you another one.

 

[Idunno]

I contacted support, and cris is sending me a replacement screen. Outstanding customer support!

 

[Idunno]

I want to post an update on this. First of all, eggfinder offers awesome support. Chris sent me a second LCD screen no questions asked, and when it didn't work assumed that I had broken something and decided to order a second RX board. Yesterday I finally got around to starting assembly on that 2nd board when a couple of things happened.
1. When starting assembly on the 2nd rx module, I noticed I was plugging the LCD screen in upside down. Since the backlighting turned on when plugged in backwards I assumed it was the correct position, but nope! Plugging in the LCD the correct orientation still had the same problem though where nothing but blocks came up.
2. I noticed a solder joint on the RF module that hadn't flowed well. As soon as I fixed that the module came to life.

It's a lot harder to destroy these boards than I thought.

Now I have two RX boards. I will assemble the 2nd one anyways because I am much better at soldering now and made a few dumb mistakes on the first one.
Also one tip for anyone else starting out: just order the suggested size conical tip in the build instructions. Initially I was using a smaller needle nose tip, and it was not able to adequately transfer heat, especially on larger surface mount pads. Even on the smaller pads solder wasn't flowing right. Just spend the extra $5-$10, it makes a world of difference.

Again, thanks to eggfinder for the outstanding support.
Question- why not use the backlighting on the display? Is it for battery life? Which pin turns on the backlighting? I might make a switch to optionally turn it on.