As Ron said, it's because you have a connection fault on one of the data lines D0-D3 to the LCD. Earlier firmware used the LCD in 4-bit mode (D4-D7) so any connection faults on D0-D3 would be hidden. But when you updated the firmware to a version which uses full 8-bit mode, you exposed the fault.?
All QMX and QMX+ PCB versions are compatible with the latest firmware versions.
On Wed, Apr 2, 2025, 05:30 Ronald Taylor via <wa7gil=[email protected]> wrote:
Randy, I think that was about when the firmware started using all 8 of the LCD data lines. Prior to then it only used 4 of them. One of the 4 others may not be soldered well. Good luck.?
Ron
On Tue, Apr 1, 2025 at 19:58 Randy K7RAN via <padawer=[email protected]> wrote:
Ok, I've figured this out.
?
Firmware versions 19 and earlier work on my QMX — every one of them back to v6 (the earliest one I tried). Thank goodness for Terminal mode.
?
Firmware versions 20 and later do not work on my unit. This was a very early unit — not sure if that matters.
?
So I asked ChatGPT (the oracle, hi hi)... and it suggests a few possibilities (pasted below).
?
Now I'm going to update my newer QMX (hopefully without trouble)! I do wonder if the older one can ever run the newer firmwares, though.
?
73, Randy K7RAN
?
? Results Recap:
Version Range
Display Status
1.00.006–1.00.019
? WORKING — screen readable
1.00.020+
? BROKEN — gibberish display
? What Likely Changed in v1.00.020?
Though QRP Labs doesn’t publish full changelogs, this kind of breakpoint often indicates:
A new display init routine
A change to font handling or character encoding
Swapping display libraries or restructuring how the OLED is accessed
It might’ve been something meant to improve performance or reduce memory usage — but it probably made assumptions about the display controller that don’t hold for yours.