XIAO ESP32S3 Plus: ADC_BAT on GPIO10?

[djholt]

I’ve got 20 of the new XIAO ESP32S3 Plus boards, and I’m trying to learn about the ADC_BAT label connected to GPIO10 on the board schematic. I was hopeful that this would allow battery voltage measurements, but I’m not seeing any connection to the battery circuit, or a voltage divider.

Am I missing anything here? I’m curious about the nature of this label in the schematic.

Thanks all!

[PJ_Glasso]

Hi there,

So this is a Great question!

On the XIAO ESP32S3 Plus, the label ADC_BAT typically refers to the battery voltage sense line, and on this board it’s connected to GPIO10, which is an analog-capable pin.

What is ADC_BAT?

• ADC_BAT is used to measure the voltage level of the battery.
• It connects to an analog input (GPIO10) that lets the ESP32S3 read the battery voltage via its internal ADC (Analog to Digital Converter).
• Often, there’s a resistor voltage divider between the battery and this pin to ensure the voltage stays within safe ADC levels (typically under 3.3V).

Why is this useful?

• It allows your code to monitor battery level.
• You can shut down peripherals or enter deep sleep when the battery gets low.
• You can display battery % on-screen or transmit it wirelessly.

Example: Read battery voltage from ADC_BAT

Here’s a simple Arduino sketch to read the voltage on GPIO10 (ADC_BAT):

const int BAT_ADC_PIN = 10;  // GPIO10 = ADC_BAT
const float ADC_REF_VOLTAGE = 3.3;  // Reference voltage
const int ADC_RESOLUTION = 4095;    // 12-bit ADC
const float VOLTAGE_DIVIDER_RATIO = 2.0;  // e.g., 100K/100K divider

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
}

void loop() {
  int adcValue = analogRead(BAT_ADC_PIN);
  float voltage = (adcValue / float(ADC_RESOLUTION)) * ADC_REF_VOLTAGE * VOLTAGE_DIVIDER_RATIO;

  Serial.print("Battery Voltage: ");
  Serial.print(voltage);
  Serial.println(" V");

  delay(1000);
}

Check the schematic for your exact resistor divider ratio if you’re unsure — some boards use 100K/100K, others may differ.

I don’t see any info on the WiKi maybe they will add some?

HTH
GL PJ

I don’t see mention of it in the Tech refrence guide , So i’m Sus.

[djholt]

Thanks PJ! This is what I had expected (and hoped for), but I don’t see any evidence that this pin is actually connected to the battery circuit or a voltage divider for measurement. Maybe something is hiding that I don’t see, but it appears to be a false advertisement in the schematic—maybe something planned initially but was never implemented?

I’m curious if there’s a way to consult the engineers or devs that designed the Plus model of the XAIO ESP32S3. Do those folks frequent these discussions?

Thanks everyone!

[PJ_Glasso]

Hi there,

Sure thing, We all want to know. So I have a couple in route so I’ll be able to put hands on and test. I couldn’t find anything even in the technical reference guide. Unlike them to to stretch that far i’m thinking…

Stay tuned
HTH
GL PJ

[djholt]

Thanks!

It seems more likely that the ADC_BAT label is a mistake in the schematic (or the label is correct but further details are missing in the schematic, which seems less likely).

DJ

[PJ_Glasso]

Hi there,

Well, if you have been around Seeed Studio devices, you know.
It’s a 50/50 proposition. Odd it’s in a few Places so , the pins spreadsheet for example? Let’s see if more info comes.

GL PJ

[djholt]

Fair enough. Yeah, I did notice the label in the pinout spreadsheet. In some instances, I know there is a requirement to write a certain pin high to enable an ADC, which may be the case here. There’s also this in the wiki for the non-Plus XIAO ESP32S3, which suggests this may have been a planned improvement for the Plus board:

[PJ_Glasso]

Hi there,
Agree it would be a smart move , or some would say " a BOLD choice"

[djholt]

Quick update: since the voltage divider circuit is not present on the board, I tested a quick battery measurement using GPIO10 and my own voltage divider with 2x220K resistors, and it works great that way.