DB48X: HP48-like RPL implementation for DM42

[c3d]

(07-03-2024 05:58 PM)spiff72 Wrote:  EDIT2: I tried flashing the latest C47 and it appears to report the same voltage with the BATT? command (around 2.49v), but that firmware doesn't pop up a message about replacing the battery. With the DB48x firmware, I can't even turn the calc off to get out of that error state.

The error state probably indicates that the calculator is off. It depends on the precise message, but what you seem to indicate is that the voltage was low enough that the firmware selected an "emergency shutdown" to preserve memory content, in which case it might not even draw the off image (because that does consume power).

I tuned the firmware thresholds based on experiments on a DM42 with various medium-quality batteries.That would probably require more experimentation and fine-tuning.

Quote:It's surprising to me that the voltage value available in the firmware differs from the voltage I can read at the battery. I will swap the battery for a better quality one when I get home tonight.

I agree with the explanation that it's the difference between voltage under load and voltage without a load.