When the new version of SerLCD 20x4 LCD with RGB backlight AND a Qwiic connecter was announced, I, uh, “Qwiicly” ordered one. I had a chance last night to hook it up to a RedBoard Artemis (it was what was at hand) via a Qwiic cable and started going through the examples. They worked fine, except that I quickly noticed that if I touched the SerLCD in the vicinity of where the headers can be soldered on the updates go bonkers.
The thought occurs to me (haven’t had time to check it out) that it might help if the inputs are declared to be “INPUT_PULLUP” in the firmwere.
Another question I have about the firmware is this: The vertical bar (0x7C) is used to signal the SerLCD to go into “settings” mode. BUT, what if I want to display a vertical bar? How do I escape it? (Yes, I realize that I could put a vertical bar into a custom character, but I’d rather keep that space available for other things.)
Sounds like you have an intermittent connection or a ground problem. Check the solder and crimp connections on all pins and leads for continuity, while wiggling the connectors.
The original testing was done with the RedBoard Artemis pulgged into one of my MacBook Pro’s USB ports, and being powered by that. (I had an Apple C->A cable, with an A->C cable plugged into that to the RBA.)
Further testing, using a USB “wall wart”, once with a USB->barrel cable and again with the aforementioned A->C cable, and repeating with a different Qwiic cable, have all yielded similar results.
To isolate the “touch point” a bit, I used a straightened paper clip, and found that display gets “extra characters” whenever I touch one of the RXI or RX pins. If I happen to touch the DTR or RST pins, the display does a reset (going through the “splash screen”) and apparently loses sync with the RBA, as I have to hit the RESET button on the RBA to get the data being displayed again.
Ever touch an audio input cable to an amp and hear a buzzing sound coming from your speakers?
Same thing is happening with the display. The serial input on these is really sensitive and when you are very near or touching the serial input, the display sees what it thinks is ‘data’ and tries to decode it resulting in craziness on the display.
As long as you’re not touching the input everything should be fine but you can “desensitize” that pin a bit by sticking a 1M ohm resistor between RX and 3.3V.
You might say that I have a “lot of resistance” to that fix… :roll: so I raised an issue (#27) for OpenLCD.
While I was there, I also read through the code and found the answer to the other question regarding the vertical bar (aka “pipe” symbol): The software will accept a second vertical bar as a character to be displayed. I’ll go and suggest adding that to at least the “cheat sheet” in the Hookup Guide.
@jremington - Your feedback is noted, not helpful, and borders on trolling. Please change your attitude or leave.
@ArizonaClark - Thanks for opening up the issue! We may be able to fix it in firmware - I’ll have to dig into the '328 datasheet to remind myself if pull ups can be enabled along side the UART hardware. If not, then your issue proposal is a sound one (non-volatile/temp disable of the various ports). I’ll post updates on the repo issue.
ordered one. I had a chance last night to hook it up to a RedBoard Artemis (it was what was at hand) via a Qwiic cable and started going through the examples. They worked fine, except that I quickly noticed that if I touched the SerLCD in the vicinity of where the headers can be soldered on the updates go bonkers.