When using the internal 1.1V reference voltage, I powered an ESP32 with 5V USB and measured a 1.5V source using one of the ADC inputs, this got me 4095 as the ADC measurement which was expected as 1.5>1.1. However, when powering the ESP32 with a 3.3V battery directly with the 3.3V port, I got an ADC…

Please do not past pictures of code. It is a waste of time as it cannot be copied for examination and testing The easier you make it to read and copy your code the more likely it is that you will get help Please follow the advice given in the link below when posting code , use code tags and post …

[image] UKHeliBob: If you get errors when compiling please copy them from the IDE using the "Copy error messages" button and paste the clipboard here in code tags My apologies, I am new to the forum and so do not have experience when asking questions. The code is below. Thanks. #include "esp…

We need to see ALL the code Andrew - please post the rest (ie your header file, functions etc.) Also please tell us if you are using an ESP32 alone, or on a development board & if so which one - as they ALL have subtle differences as explained in this link [image] Getting Started with the…

[image] johnerrington: We need to see ALL the code Andrew - please post the rest (ie your header file, functions etc.) Also please tell us if you are using an ESP32 alone, or on a development board & if so which one - as they ALL have subtle differences as explained in this link Sorry, I hav…

[image] andrewkeir: #include "esp_adc_cal.h" The code you have posted is useless without the include file. Can you attach it please?

Hi, sorry again, I have attached the header file. I believe the specific function used is defined in this library ( https://github.com/espressif/esp-idf/blob/master/components/driver/adc_common.c ). I was following the information available at Page not Found - ESP32 - — ESP-IDF Programming Guide lates…

Hi Andrew: IMHO you are making life very hard for yourself (and us :wink: ) its very easy to read the analog voltage with an ESP32 without all that additional code. Here is an example I have tested with a pot connected between 0V and 3.3V, slider to GPIO34 (adapted from ESP32 Analog Input with Ar…

Hi, thanks for your help. I have adapted some of your code to test my configuration but the problem still exists where when I have a battery powering the ESP32, connected directly to the 3.3V pin, the ADC reading is constantly fluctuating from 0 to 4095 whereas with the USB connected and powering th…

[image] andrewkeir: analogSetAttenuation(ADC_0db); sets no attenuation. ADC can measure up to approximately 800 mV (1V input = ADC reading of 1088). I'd suggest you leave the default settings - just comment these out [image] andrewkeir: //Using UART to send the ADC reading to another E…

[image] andrewkeir: I am using a CR123A lithium battery which should produce enough current as I have already tested the ESP32s WiFi functionality whilst being powered by the battery, this uses roughly 110mA. Did you forget the ~500mA and ESP draws during short transmit peaks. That could dro…

How to measure voltage of battery using ESP32 internal reference voltage?

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How to measure voltage of battery using ESP32 internal reference voltage?

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