Qball's Weblog
Hitting a new low-power record with the esp32c3
When looking up some information I blogged about in the past, I realized I haven’t posted any updates in ages. A while back I switched to esp32s2 and got some nice result out of this single core chip. However espressif in there wisdom decided to stop producing the esp32s2-wroom and marking it NRND. This must be their shortest lived SoM. The did release the esp32c3, this is another single core chip, with a RiscV running at 160MHz. I think it is a step down from the esp32s2; less hardware modules (f.e. One that I used for 1 wire protocol), no ulp, bluetooth (that I don’t need), needs more external components and less pins on the wroom module.
On the positive side, its been very reliable, allows for some tiny pcb design and get low deep-sleep consumption. On my test-print it goes to ~7µA usage in idle (this includes with a 2MΩ divider for measuring battery voltage). This together with a good espnow implementation makes it extremely low power. For a quick every 2 minutes ‘ping I am here’, I get a ~94µAh usage.
But if we zoom in, we do see a fairly high spike, making battery selection tricky:
Given I switched to LifePO4 batteries, even with the lower capacity, I still get years battery lifetime.
To use the module I’ve designed a little PCB, that works for both LifePO4 or LI-ION batteries (I do undervoltage in software for LifePO4 or use protected cells for LI-ION):
Or soldered (v0.2):
