Flashing the ESP32

This guide explains how to flash the ESP32 module on the Nagami module. The ESP32 provides Wi-Fi and Bluetooth using ESP-Hosted-NG firmware from Espressif.

⚠️ The ESP32 is connected via SDIO, and its strapping pins are controlled by both the MMC host and the mmc-pwrseq driver. You must fully release both before flashing.

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Prerequisites

Ensure the following are available on the Nagami module:

• esptool.py, espefuse.py, espsecure.py
• A valid ESP-Hosted-NG firmware build (see build section below)

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Step-by-Step Instructions

Step 1: Disable ESP32 Control (MMC + PWRSEQ)

Since the driver is now managed by udev, there is no service to stop. Instead, manually release control:

# Unbind MMC host
echo "4021000.mmc" > /sys/bus/platform/drivers/sunxi-mmc/unbind

# Unbind power sequence (IMPORTANT - releases reset GPIO)
echo "wifi-pwrseq" > /sys/bus/platform/drivers/pwrseq_simple/unbind

👉 Both steps are required. Unbinding MMC alone is not sufficient.

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Step 2: Enter ESP32 Bootloader Mode

Set the strapping pins and reset the ESP32:

gpioset -t0 ESP_nBOOT=0
gpioset -t0 ESP_D0=0

# Reset pulse
gpioset -t0 ESP_nRST=0
gpioset -t0 ESP_nRST=1

The ESP32 is now in UART bootloader mode.

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Step 3: (Optional) Set Flash Voltage

If using a new or replaced ESP32, set flash voltage to 3.3V:

espefuse.py -p /dev/ttyS1 -b 115200 --chip esp32 set_flash_voltage 3.3V

⚠️ This is one-time and irreversible. Type BURN when prompted.

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Step 4: Flash Firmware

Run:

esptool.py -p /dev/ttyS1 -b 115200 --chip esp32 write_flash \
  --flash_mode dio --flash_size detect --flash_freq 40m \
  0x1000 bootloader.bin \
  0x8000 partition-table.bin \
  0xd000 ota_data_initial.bin \
  0x10000 network_adapter.bin

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Step 5: Reboot System

After flashing:

reboot

✅ On boot, udev will automatically:

• Rebind MMC
• Reattach mmc-pwrseq
• Load ESP-Hosted driver

You should see WiFi come up (“✨ look at the stars”).

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Building ESP-Hosted-NG Firmware

If you need to build firmware manually:

git clone https://github.com/espressif/esp-hosted.git
cd esp-hosted

# Checkout version matching kernel module
git checkout release/ng-1.0.5.0.3

Build

cd esp_hosted_ng/esp/esp_driver

./setup.sh
. ./esp-idf/export.sh

idf.py set-target esp32
idf.py build

Output Files

After building, use:

build/bootloader/bootloader.bin
build/partition_table/partition-table.bin
build/ota_data_initial.bin
build/network_adapter.bin

Copy them to the Nagami module (e.g. via scp) and flash using the steps above.