max voltage for ADC(0)?

All ESP8266 boards running MicroPython.
Official boards are the Adafruit Huzzah and Feather boards.
Target audience: MicroPython users with an ESP8266 board.
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oyster
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max voltage for ADC(0)?

Post by oyster » Tue Feb 16, 2021 1:59 pm

8. Analog to Digital Conversion says
Please note that this input can only tolerate a maximum of 1.0 volts
while esp8266-adc-reading-analog-values-with-nodemcu says
The ESP8266 ADC pin input voltage range is 0 to 1V if you’re using the bare chip. However, most ESP8266 development boards come with an internal voltage divider, so the input range is 0 to 3.3V. So, in sumary:

-ADC Voltage range in ESP8266 development boards: 0 to 3.3V (for example: ESP8266 12-E NodeMCU Kit, WeMos D1 Mini, …)
-ADC Voltage range in ESP8266 chip: 0 to 1V (for example: ESP-07 chip, ESP-12E chip, …)
if so, is it better to mention the later one in 8. Analog to Digital Conversion?

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Roberthh
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Re: max voltage for ADC(0)?

Post by Roberthh » Tue Feb 16, 2021 2:55 pm

I do not agree to the statement "most ESP8266 development boards"
It's more like "some ESP8266 development boards". Next to the listed ones for instance all Adafruit and Sparkfun boards come without voltage divider.

kevinkk525
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Re: max voltage for ADC(0)?

Post by kevinkk525 » Tue Feb 16, 2021 2:58 pm

So the expensive versions have no voltage divider and all the cheap chinese ones do? That's interesting.. But I'd say most of the boards are chinese versions and those (afaik) have voltage dividers. At least all my NodeMCUs do.
Kevin Köck
Micropython Smarthome Firmware (with Home-Assistant integration): https://github.com/kevinkk525/pysmartnode

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Roberthh
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Re: max voltage for ADC(0)?

Post by Roberthh » Tue Feb 16, 2021 3:16 pm

Without the pre-built voltage divider you have more design choices when using it.
Adding the voltage divider is a valued attempt of protecting against wrong use. Especially all inputs then have the same voltage range.

P.S.: I would call all NodeMCU variants 1 model, which is made by various sources

kevinkk525
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Re: max voltage for ADC(0)?

Post by kevinkk525 » Tue Feb 16, 2021 4:31 pm

Yeah you're probably right. They might protect themselves against claims from people using the ADC wrong and frying their chips.

PS: Absolutely, the nodeMCU is the same design from multiple manufactures. (Which is actually something nice with the esp8266 because it makes it easy to work with the same board whereas there are so many esp32 boards, you can't even design a PCB for a common esp32 board because there are so many..)
Kevin Köck
Micropython Smarthome Firmware (with Home-Assistant integration): https://github.com/kevinkk525/pysmartnode

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