6 ms·

I wonder if the power consumption is any better. An nRF runs circles around any existing ESP32 variants in terms of power.

KennyBlanken 1y ago
Not to mention the horrific peak power draw. It took people a while to figure out that the things need a fair bit of close-by capacitance on the power rail or they crash.
- stavros 1y ago
  How much capacitance? I built my own sensors based on ESP8266 and they've been flaky, and I wonder whether that's the issue.
  - wwarren 1y ago
    Coming out of deep sleep and Wifi coming back up, I’ve seen upwards of 600mA
    - stavros 1y ago
      Wow, jeez, no wonder the USB won't power it...
      - xobs 1y ago
        That's 600 mA at 3.3V. USB should be fine, but of course you need the capacitance to deal with that. Radio PAs can be power-hungry beasts.
    - obitsten 1y ago
      The annoying thing is this is only due to "calibration" which can, with some highly esoteric optimisations, be skipped. Depending on the application , this can realise massive gains in peak power, wakeup latency, and even average power. The whole process is hidden in a binary blob though and espressif will not elaborate on it, so it's very challenging to alter.
  - XorNot 1y ago
    220uf would be the minimum. I've had modules get stuck in a boot loop when they have less then 120uf (inferred by repairing switch modules with bad capacitors).
    - londons_explore 1y ago
      Usually you can fix it in software too. For example, put a sleep(100us) as a hook before packet transmission to allow capacitors to recharge between packets. Had to do this on a design powered by a cr2032 because the peak power draw from those batteries is really limited.
      - brokenmachine 1y ago
        How many seconds of ESP32 power do you get from that cr2032?
        mort96 1y ago
        A cr2032 has somewhere around 200mAh. The low-power ESP32-C3 uses somewhere around 20mA when its radios are off but the CPU is running and peripheral clocks are running, which gives a roughly 10 hour runtime. This calculation ignores the fact that the battery's voltage will drop below where the ESP browns out before it has delivered all its power (or assumes that it's regulated up at perfect efficiency), but most cr2032 batteries are a bit above 200mAh so it probably mostly evens out. Though note that for most of its life, the cr2032 will deliver slightly below the ESP's minimum spec of 3V. From experience, that's not really an issue. If you can get away with spending most of your time in the ESP's deep sleep state however, battery life is gonna be way better, and that's probably what you'd want to do if you're using a cr2032. In deep sleep, the ESP32-C3's data sheet says it consumes around 5µA (0.005mA). With 200mAh, this gives a battery life of 40 000 hours, or 4.5 years. At those time scales, battery self-discharge becomes relevant, so let's say a couple of years. So a decent mental model is: you can do a few hours of cumulative compute over the course of a couple of years. Unless you decide to boost the voltage of the cr2032 to be within the ESP's spec. In that case, the whole deep sleep discussion might be moot; I suspect the regulator's own power draw would absolutely dominate the 5µA of the ESP. But I'm not super familiar with the world of power regulators, maybe there are ultra low power regulators which can do the job with minimal losses even in the µA regime.

KennyBlanken 1y ago

Not to mention the horrific peak power draw. It took people a while to figure out that the things need a fair bit of close-by capacitance on the power rail or they crash.

stavros 1y ago
How much capacitance? I built my own sensors based on ESP8266 and they've been flaky, and I wonder whether that's the issue.
- wwarren 1y ago
  Coming out of deep sleep and Wifi coming back up, I’ve seen upwards of 600mA
  - stavros 1y ago
    Wow, jeez, no wonder the USB won't power it...
    - xobs 1y ago
      That's 600 mA at 3.3V. USB should be fine, but of course you need the capacitance to deal with that. Radio PAs can be power-hungry beasts.
  - obitsten 1y ago
    The annoying thing is this is only due to "calibration" which can, with some highly esoteric optimisations, be skipped. Depending on the application , this can realise massive gains in peak power, wakeup latency, and even average power. The whole process is hidden in a binary blob though and espressif will not elaborate on it, so it's very challenging to alter.
- XorNot 1y ago
  220uf would be the minimum. I've had modules get stuck in a boot loop when they have less then 120uf (inferred by repairing switch modules with bad capacitors).
  - londons_explore 1y ago
    Usually you can fix it in software too. For example, put a sleep(100us) as a hook before packet transmission to allow capacitors to recharge between packets. Had to do this on a design powered by a cr2032 because the peak power draw from those batteries is really limited.
    - brokenmachine 1y ago
      How many seconds of ESP32 power do you get from that cr2032?
      - mort96 1y ago
        A cr2032 has somewhere around 200mAh. The low-power ESP32-C3 uses somewhere around 20mA when its radios are off but the CPU is running and peripheral clocks are running, which gives a roughly 10 hour runtime. This calculation ignores the fact that the battery's voltage will drop below where the ESP browns out before it has delivered all its power (or assumes that it's regulated up at perfect efficiency), but most cr2032 batteries are a bit above 200mAh so it probably mostly evens out. Though note that for most of its life, the cr2032 will deliver slightly below the ESP's minimum spec of 3V. From experience, that's not really an issue. If you can get away with spending most of your time in the ESP's deep sleep state however, battery life is gonna be way better, and that's probably what you'd want to do if you're using a cr2032. In deep sleep, the ESP32-C3's data sheet says it consumes around 5µA (0.005mA). With 200mAh, this gives a battery life of 40 000 hours, or 4.5 years. At those time scales, battery self-discharge becomes relevant, so let's say a couple of years. So a decent mental model is: you can do a few hours of cumulative compute over the course of a couple of years. Unless you decide to boost the voltage of the cr2032 to be within the ESP's spec. In that case, the whole deep sleep discussion might be moot; I suspect the regulator's own power draw would absolutely dominate the 5µA of the ESP. But I'm not super familiar with the world of power regulators, maybe there are ultra low power regulators which can do the job with minimal losses even in the µA regime.