Ok, I've figured this out.
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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.
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Firmware versions 20 and later do not work on my unit. This was a very early unit — not sure if that matters.
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So I asked ChatGPT (the oracle, hi hi)... and it suggests a few possibilities (pasted below).
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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.
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73, Randy K7RAN
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? 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:
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A new display init routine
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A change to font handling or character encoding
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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.
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Randy K7RAN