HT16K33 I²C address

How to set the address

Wire the address pins like this:

A2 A1 A0 → 0x70–0x77

Only the 28-pin version has all three address pins (0x70–0x77); the 24-pin version has A1 and A0 (0x70–0x73) and the 20-pin version is fixed at 0x70. The pins double as ROW outputs: left open they read 0, and a 1 takes a diode and a resistor, as in the datasheet.

Devices that use the same addresses

Two devices on the same bus can’t answer on the same address. These modules from our list use at least one of these addresses:

If two of them end up on the same address, move one with its address pin, put one behind a TCA9548A multiplexer (0x70–0x77), or use a second I²C bus: the ESP32, ESP32-S3 and RP2040 have two I²C controllers (the ESP32-C3 has one).

Check your whole bus →Add the HT16K33 and your other modules: the checker finds conflicts, suggests free addresses and sizes the pull-ups.

7-bit and 8-bit address

I²C addresses are 7 bits long. Some datasheets and libraries write them as 8-bit numbers, with the read/write bit added on the right: that is why the same chip can appear as 0x70 or 0xE0. Arduino’s Wire library and ESPHome use the 7-bit form.

Check that it answers

Upload this sketch with the HT16K33 wired to SDA and SCL: it tries every address the chip can use and prints the one that answers. On an ESP32 the default pins are GPIO21 (SDA) and GPIO22 (SCL); on an Arduino Uno, A4 and A5.

#include <Wire.h>

const byte ADDRS[] = {0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77};

void setup() {
  Serial.begin(115200);
  Wire.begin();
  for (byte a : ADDRS) {
    Wire.beginTransmission(a);
    if (Wire.endTransmission() == 0) {
      Serial.print("HT16K33 answers at 0x");
      if (a < 0x10) Serial.print('0');
      Serial.println(a, HEX);
      return;
    }
  }
  Serial.println("No answer: check the wiring");
}

void loop() {}

In ESPHome the bus is scanned at boot (scan: true is the default): the log lists every address that answers.

i2c:
  sda: GPIO21
  scl: GPIO22
  scan: true

Pull-up resistors

SDA and SCL need pull-up resistors to the supply. Many breakout boards already carry them, often 4.7 kΩ or 10 kΩ, and with several boards on the bus they add up in parallel. The I²C checker works out the allowed range for your bus voltage and speed.

Similar devices

SH1106 SSD1306 SSD1309

Addresses checked against the HT16K33 datasheet.