Lopy4 - 3.3V out disable?
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Lopy4. Is it possible to switch off the power supply out on pin 3.3V during machine.deepsleep() in order to not power sensors?
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Are you using a pytrack or pysense or just the Lopy4?
The Pytrack / Pysense have seperate 3.3v pins for both sensors and the mainboard for exactly this reason.
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Just Lopy4 alone (or with expansion board 3).
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@giorgio Then sadly its not possible to switch the 3v3 pin off on the module. if the module is powered the pin has power and there's no way to turn it off doing so would also shutdown power to the ESP.
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@giorgio How much power do you need? It may be possible to power the sensor directly with any of the GPIO pins if you don't need too much (the limit is 12 mA per pin, and 6 mA is recommended). Otherwise you'll probably need to add a transistor using both.
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@jcaron great idea... I have hx711 (load cell) ... that more or less need 1.5ma. So I could power the hx711 directly from a GPIO?!
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@giorgio I'm not a hardware guy, so I may be missing something, but it looks like it. I have no idea if there are any ill effects from having a constant 1.5 mA draw on one the GPIO pins, though.
Wait for confirmation from someone who is more competent than I am on the hardware side :-)
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@jcaron The ESP32 data sheet https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf says high level source current IOH is 20 or 40 mA, depending on domain. The voltage will probably be quite noisy as it comes from the digital supply of the ESP32. The HX711 is a 24 bit sigma delta front end for load cells. For optimal performance, I'd power this from a separate regulator, but try it... If you look at the data sheet
https://www.mouser.com/ds/2/813/hx711_english-1022875.pdf
you see it has an internal analog regulator. Running from a 3.3 V supply, I'd set the analog voltage to 3.0 V, which would at least reduce the noise.
Also note that the IO driver of the ESP32 (or any digital device) has a much higher resistance than an external FET switch you'd typically use (there are no specs on this in the datasheet), introducing additional errors.
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