SOLVED! Solution begins at this post.
I just finished building the Module Tester (v2 pcb) and the board appears to work after flashing the MCU but I’m not seeing any text on the LCD. The LCD backlight comes on and if I crank the contrast up high I can see all of the dots inside each of the 16x2 rectangles. I’m using the exact LCD specified in the BOM. Yet, I don’t see any text / menu on the LCD no matter where I adjust the Contrast. The only time I see text is if I pull the MCU and power up the LCD, then I see a cursor on the far right position of the top line.
Things I’ve checked:
- Continuity between LCD pins and the MCU and other points on the PCB: YES
- Both lines on LCD light up with contrast at max: YES
- Reflowed solder of the Contrast Trimmer: YES
- Buttons light up corresponding LEDs when pressed: YES
- I hear sound from Audio Out, Gate Out, and Clk Out: YES
I also did the LCD troubleshooting steps from the Wiki.
Here’s what I’m measuring on the LCD pins:
2 = 5V
3 = 5V if LCD contrast at zero, 0V if LCD contrast at max
4 = 8.3mV
5 = 0V
6 = 2.7V
7/8/9/10 = 4.98V (but not connected to anything on the board)
11 = 7.0mV
12 = 6.6mV
13 = 5.6mV
14 = 2.5V
15 = 5V
I also tried a second LCD (from some Shruthi-1 BOM that I haven’t built yet) and it doesn’t show any menu text either. I’ve inspected the board with a microscope and I don’t see any faults. My soldering skills are A+.
At this point I’m kinda stumped why I can’t see the menus… I’m not sure what else I should be checking. None of the previous forum posts about non-functioning LCDs have been helpful, as I don’t appear to have the same problem.