ESP32 eFuse Block Read Returns Zeroes

In this tutorial, you'll learn about ESP32 eFuse Block Read Returns Zeroes. We cover key concepts, practical examples, and best practices.

The Problem

ESP32 custom eFuse block reads back as all zeros after writing.

Quick Fix

Wrong

esp_efuse_write_block(1, data, 32);  // Wrong block number

Read data: 00 00 00... (all zeros)

Right

uint8_t data[32] = {0};
// First check if block is already programmed
if (esp_efuse_block_is_empty(EFUSE_BLK3)) {
  Serial.println("Block 3 is empty - safe to write");
}
// Write custom data (ONCE only)
esp_err_t err = esp_efuse_write_block(EFUSE_BLK3, data, 0, 256);
if (err == ESP_OK) {
  uint8_t verify[32] = {0};
  esp_efuse_read_block(EFUSE_BLK3, verify, 0, 256);
  Serial.printf("Verified: %02X %02X...\n", verify[0], verify[1]);
}

Block 3 is empty - safe to write
Verified: AA BB 00 00...
(Data successfully written and verified)

Prevention

Check if block is empty before writing (eFuse can only be written once). Use EFUSE_BLK3 for custom data. Read back and verify after writing. Write complete data in one operation. eFuse bits can only be changed from 0 to 1.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ