Boost voltage

[Tugdual]

(06-06-2015 06:09 AM)Graan Wrote:  Hello
Dave Jones at EEVBlog made a video about this 2 days ago , quite interesting

https://youtu.be/4iEshd6izgk

/Andreas

Interesting indeed but Lord, I couldn't hear that guy for 30mn.

(06-05-2015 09:17 PM)Claudio L. Wrote:  I tested this last year. I don't remember exact values, but roughly these were the ballpark numbers:
The calculator idles in a "slow" clock, and jumps to a faster clock on demand.
I think for aklalines (nominal 6V) it was around 4.4V was still "safe", because when the turbo mode kicked in, the voltage dropped to about 3.8V and was still OK.
For rechargeables (nominal 4.8V), 4.0V was "safe", with voltage dropping to 3.5V or so on demand.
When voltage was around 3.3V the CPU would reset randomly.
But this is for bare minimum hardware. I didn't test if for example writing to flash could be achieved with only 4.0V, as it may drain more current. Also I didn't test if an SD card could function properly (voltage wise probably OK since they switch to their own voltages anyway, but current wise... may read OK but not write for example).

That the CPU can function doesn't mean is 100% safe, as I didn't test a worst-case scenario by any means.

I measured this using newRPL firmware, which has "slow" mode at 6 MHz and with the CPU in IDLE mode (Wait for interrupt), so it's supposed to drain less current than the stock firmware (12MHz with the CPU fully awake). On the other hand, the "fast" mode is 192 MHz (vs. 75 MHz stock), that's why the voltage drops are so steep.

Thanks Claudio. This means we can operate safely until about 1V which is aligned with the video and is a very good news. Do you by chance know how the battery indicator reacts to voltage?