And still it keeps on going

Post here to share useful tips and tricks, to ask questions about using your DM42 or to report software-related problems
toml_12953
Posts: 436
Joined: Wed May 03, 2017 5:46 pm
Location: Malone, NY USA

Re: And still it keeps on going

Post by toml_12953 » Sun May 06, 2018 7:50 pm

Russel wrote:
Sun May 06, 2018 6:49 pm
grsbanks wrote:
Sun May 06, 2018 7:17 am
[...]I was deliberately running the battery down to see how the machine behaved with such a low power supply.
Is 1.90 volts the lowest you have seen? Have you replaced the battery yet? You know what they say about the curiosity and the cat...
"How low can you go?" - Limbo Rock sung by Chubby Checker
Tom L

आपका दिन शुभ हो
DM42 SN: 00025 (Beta)
SN: 00221 (Shipping)

grsbanks
Posts: 665
Joined: Tue Apr 25, 2017 9:23 am
Location: Preston, Lancs, UK

Re: And still it keeps on going

Post by grsbanks » Mon May 07, 2018 7:19 am

LOL :)

Yes, I did replace the battery after that.

Not only did I want to see how the machine behaved with so little power available but I also wanted to see something that I'm surprised nobody else picked up on. Look at the battery icon in that screenshot... Having seen the source code for how the system chooses which icon to display depending on battery voltage, I knew there was a provision for a 7th icon that represents something more dire than the "empty" battery. So there is it, a sqeezed battery :)

This also uncovered a "bug" that only hit me yesterday while thinking of this... Operations that cause a write to the QSPI chip are all protected so that they don't happen if there's less than 2.2V across the battery. If the thing were to shut down partway through a write operation, it would cause data corruption. So, how come I was able to take a screenshot with there being only 1.9V there?

It turns out, that specific write operation is not (yet!) protected...
Not SwissMicros staff, just an enthusiast.

User avatar
Russel
Posts: 14
Joined: Fri Mar 16, 2018 7:38 pm
Location: USA

Re: And still it keeps on going

Post by Russel » Thu May 10, 2018 4:53 pm

grsbanks wrote:
Mon May 07, 2018 7:19 am
[...] Having seen the source code for how the system chooses which icon to display depending on battery voltage, I knew there was a provision for a 7th icon that represents something more dire than the "empty" battery. So there is it, a sqeezed battery :)
I noticed that...something to avoid when your calculations are mission critical! (I did suffer a fit of laughter when I saw the icon. :lol: )
grsbanks wrote:
Mon May 07, 2018 7:19 am
This also uncovered a "bug" that only hit me yesterday while thinking of this... Operations that cause a write to the QSPI chip are all protected so that they don't happen if there's less than 2.2V across the battery. If the thing were to shut down partway through a write operation, it would cause data corruption. So, how come I was able to take a screenshot with there being only 1.9V there?

It turns out, that specific write operation is not (yet!) protected...
Nice catch!

Post Reply