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FEATURE REQUEST Voltage Monitor
#1
Section 28.3 (SAR ADC) of the ESP32 Technical Reference Manual indicates that there is a channel for internal voltage (vdd33).
Is it possible to expose the vdd33 value?  I'm looking for a solution to monitor battery state on a Lolin32.
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#2
(03-05-2018, 06:57 PM)rdagger Wrote: Section 28.3 (SAR ADC) of the ESP32 Technical Reference Manual indicates that there is a channel for internal voltage (vdd33).
Is it possible to expose the vdd33 value?  I'm looking for a solution to monitor battery state on a Lolin32.

VDD33 channel is accessible via ADC2 which is not yet supported in MicroPython because it is not yet fully supported in esp-idf.
Full support for ADC2 in esp-idf is expected soon, then it will be implemented in MicroPython ADC module too.
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#3
Recently, I have also been thinking about a way to detect battery undervoltage.
Since there is no circuitry available on the M5Stack to do this, and my ESP32 will remain in deepsleep most of the time, I am doing it the hardware way with the following simple circuit:
[Image: bsdXf.png]
I could not source the SG3546, so I will be using the KA75330 instead.
[Image: 3428-00.jpg]

LEDs are not made all the same. High intensity LEDs with a higher maximum current rating are usually more efficient at sub 1mA current levels than their low current counterparts. Here is a good reading about LEDs at low currents.
73 de Serge, ON4AA   http://hamwaves.com/iot/
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#4
If you need to measure the battery voltage, you can use a simple voltage divider of 2x50 K.
If you need a low power operation, you can use a simple (enough) circuit like the one described on ESP32 forum

[Image: Bat_voltage.png]
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#5
(03-05-2018, 08:53 PM)lobo Wrote: VDD33 channel is accessible via ADC2 which is not yet supported in MicroPython because it is not yet fully supported in esp-idf.
Full support for ADC2 in esp-idf is expected soon, then it will be implemented in MicroPython ADC module too.

I noticed that you added support for ADC2.  Can VDD33 now be polled?  Does Wi-Fi use preclude use of ADC2?
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