XIAO ESP32C5

We ran a XIAO ESP32C5 on the bench with arduino-esp32 3.3.11 and read everything back over its native USB serial port.

• The serial monitor works with the Arduino menu left at its defaults: USB CDC On Boot ships Enabled.
• The user LED is GPIO27 and lights when the pin is driven LOW.
• Flash reports 8388608 bytes. PSRAM reports 0 bytes on the default menu and 8388608 bytes with Tools > PSRAM > Enabled.
• Battery sense: with GPIO26 LOW the ADC on GPIO6 reads 0 mV; with it HIGH it reads half the BAT+ voltage.
• Without an antenna a Wi-Fi scan found 3 networks, all around -93 dBm. With the bundled FPC antenna it found 20, and our router's 5 GHz SSID came in within a few dB of its 2.4 GHz signal.

Not tested here: 5 GHz range through walls, deep-sleep current, Zigbee and Thread. Those figures come from Seeed's and Espressif's documentation.

The ESP32-C5 is the first Espressif chip that can join a 5 GHz network. The practical win is not speed - it is a clean channel. In a building where every neighbour's router sits on 2.4 GHz, a 5 GHz link drops far fewer packets and keeps latency steady. The trade-off is range: 5 GHz does not pass through walls as well, so a device two rooms away may still be better off on 2.4 GHz.

Two things to get right: the external antenna you attach must be dual-band (a 2.4 GHz-only antenna will connect on 2.4 GHz and struggle on 5 GHz), and your access point must broadcast the same SSID on both bands or you pick the band by SSID. One thing to check before judging 5 GHz range: Seeed's C5 spec table lists the bundled FPC antenna as a 2.4 GHz (2.9 dBi) part, while Seeed's listing for that same antenna (FPC Antenna A-01 for XIAO ESP32C3/C5, SKU 318020748) calls it a 2.4 GHz/5 GHz combo. If 5 GHz is weak, the antenna is the first thing to swap.

In arduino-esp32 3.3 the sketch code is unchanged - WiFi.begin() picks the band - and WiFi.setBandMode() lets you pin it to 5 GHz or 2.4 GHz only.

A 3.7 V lithium cell solders to the pads on the back, and the board can measure it. Seeed's wiki: the XIAO ESP32C5 carries the SGM40567 charging chip plus a TPS22916CYFPR load switch for voltage acquisition, so the divider only draws current when you ask it to.

• BAT_VOLT_PIN is GPIO6 - the ADC input that sees the divided cell voltage.
• BAT_VOLT_PIN_EN is GPIO26 - drive it HIGH to switch the measurement circuit on.
• The divider is two 100K resistors, so the reading is half the cell voltage - multiply by 2.

#include <Arduino.h>

void setup() {
  Serial.begin(115200);
  pinMode(BAT_VOLT_PIN, INPUT);           // ADC input
  pinMode(BAT_VOLT_PIN_EN, OUTPUT);
  digitalWrite(BAT_VOLT_PIN_EN, HIGH);    // enable the measurement circuit
}

void loop() {
  uint32_t Vbatt = 0;
  for (int i = 0; i < 16; i++) {
    Vbatt += analogReadMilliVolts(BAT_VOLT_PIN);   // read and accumulate
  }
  float Vbattf = 2 * Vbatt / 16 / 1000.0;   // 1:2 divider, mV to V
  Serial.println(Vbattf, 3);
  delay(1000);
}

The module's 8 MB of PSRAM is disabled in arduino-esp32's default menu for this board. Set Tools → PSRAM → "Enabled" or ESP.getPsramSize() reports 0 and any large allocation fails. We measured it on a board here with arduino-esp32 3.3.11: 0 bytes on the default menu, 8388608 bytes once enabled.