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Arduino MKR series, Arduino Zero or compatibles, based on SAMD21 or SAMD51 MCU’s with at least 8 Kbytes of SRAM and 16 Kbyte of flash, working at 3.3 volt.
The MCU should have native USB for PC connection and hardware UART for connection to ESP, for best performance, like the SAMD-based MCU’s have.
(ESP pinout diagram by blinkmaker on www.instructables.com/Flash-or-Upgrade-Firmware-on-ESP8266-ESP-01-Module/
Connect the ESP8266 (ESP-01) to the Arduino like this:
Arduino pin |
ESP8266 (ESP-01) pin |
Purpose |
8 (D8) |
CH_PD / EN (the marking differ) |
Chip select / Chip enable signal. Used to enable and reset the ESP. |
9 (D9) |
GPIO0 |
Select flashing mode in ESP. |
10 (D10) |
RESET |
ESP reset. |
RX (13 on MKR) |
TX |
Serial |
TX (14 on MKR) |
RX |
Serial |
GND |
GND |
Ground |
VCC (3.3V / 3V3) |
3V3 |
3.3V power |
Firmware may be found at https://www.espressif.com/en/support/download/at.
Content of firmware download from espressif:
Filename Size
ESP8266_NonOS_AT_Bin_V1.7.4\.DS_Store 8196
ESP8266_NonOS_AT_Bin_V1.7.4\ESP8266 NonOS AT Release Note.pdf 117598
ESP8266_NonOS_AT_Bin_V1.7.4\bin\.DS_Store 10244
ESP8266_NonOS_AT_Bin_V1.7.4\bin\blank.bin 4096
ESP8266_NonOS_AT_Bin_V1.7.4\bin\boot_v1.7.bin 4080
ESP8266_NonOS_AT_Bin_V1.7.4\bin\esp_init_data_default_v08.bin 128
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\.DS_Store 8196
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\README.md 2182
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\1024+1024\user1.2048.new.5.bin 413444
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\1024+1024\user2.2048.new.5.bin 413444
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\512+512\user1.1024.new.2.bin 413444
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\512+512\user2.1024.new.2.bin 413444
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at_sdio\README.md 1764
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at_sdio\1024+1024\user1.2048.new.5.bin 461732
ESP8266_NonOS_AT_Bin_V1.7.4\bin\at_sdio\1024+1024\user2.2048.new.5.bin 461732
First part of ESP8266_NonOS_AT_Bin_V1.7.4\bin\at\README.md:
# Notice: AT firmware becomes larger since it supports more functions. So, we provide two firmwares here: * 1024+1024: Normal AT, which is compiled from ESP8266_NONOS_SDK/examples/at, and uses mbedTLS lib. * 512+512: Nano AT, which is compiled from ESP8266_NONOS_SDK/examples/at_nano, and uses SSL lib that supports less cipher suites. It is suggested to use normal AT(1024+1024), if your flash size is 2MB or larger. # BOOT MODE ## download ### Flash size 8Mbit: 512KB+512KB boot_v1.2+.bin 0x00000 user1.1024.new.2.bin 0x01000 esp_init_data_default.bin 0xfc000 blank.bin 0x7e000 & 0xfe000 ### Flash size 16Mbit-C1: 1024KB+1024KB boot_v1.2+.bin 0x00000 user1.2048.new.5.bin 0x01000 esp_init_data_default.bin 0x1fc000 blank.bin 0xfe000 & 0x1fe000
For an ESP8266 with 8 Mbit / 1 Mbyte flash, configure the ESP8266 Download Tool according to the information from the README.md file like below. Some deduction must be done, to find the correct files:
| Text from README.md | Remark | Firmware file | Start address |
| boot_v1.2+.bin 0x00000 | This means to choose a file with bootloader with version 1.2 or newer | bin\boot_v1.7.bin | 0x0 |
| user1.1024.new.2.bin 0x01000 | Finds this file in the 512+512 folder | bin\at\512+512\user1.1024.new.2.bin | 0x1000 |
| esp_init_data_default.bin 0xfc000 | Matches with esp_init_data_default_v08.bin | bin\esp_init_data_default_v08.bin | 0xfc000 |
| blank.bin 0x7e000 & 0xfe000 | With two start addresses, this file must be flashed into two addresses | bin\blank.bin | 0x7e000 |
| bin\blank.bin | 0xfe000 |
For an ESP8266 with 16 Mbit / 2 Mbyte flash, configure the ESP8266 Download Tool according to the information from the README.md file like below. Some deduction must be done, to find the correct files:
| Text from README.md | Remark | Firmware file | Start address |
| boot_v1.2+.bin 0x00000 | This means to choose a file with bootloader with version 1.2 or newer | bin\boot_v1.7.bin | 0x0 |
| user1.2048.new.5.bin 0x01000 | Finds this file in the 512+512 folder | bin\at\1024+1024\user1.2048.new.5.bin | 0x1000 |
| esp_init_data_default.bin 0x1fc000 | Matches with esp_init_data_default_v08.bin | bin\esp_init_data_default_v08.bin | 0x1fc000 |
| blank.bin 0xfe000 & 0x1fe000 | With two start addresses, this file must be flashed into two addresses | bin\blank.bin | 0xfe000 |
| bin\blank.bin | 0x1fe000 |
If having a flash of 16 Mbit or more or wanting to use the AT-SDIO version for 16 Mbit flash, refer to the ESP8266_NonOS_AT_Bin_V1.7.4\bin\at_sdio\README.md file.
The ESP firmware flashing tool may be downloaded from https://www.espressif.com/en/support/download/other-tools.
Unpack and run the flash download tool:
A black window appears.
Select Developer Mode
Select ESP8266 DownloadTool
Use SpiAutoSet to get parameters from ESP, by checking SpiAutoSet and pressing START with no files selected for flashing. Filenames may be listed, but they must be unchecked.
When using an Arduino MKR or Zero, baud rate could be set at up to 1500000 baud. If using an Arduino without native USB, 115200 should be used, and PASSTHROUGH_MODE should be set to FlashingMode in the sketch.
The command window shows the working. Initially the flashing program connect using 115200 baud, sending a stub loader to the ESP. If another baud rate than 115200 is selected in the user interface, the baud rate is switched. Switching baud rates will only work for Arduinos with native USB connection to the PC, since they in fact ignore the baud rate between the PC and Arduino, always running at full USB speed, which for an SAMD21 is 12 Mbit/sec. The EspSerialPassthrough sketch detects the baud rate change command, and changes the baud rate between the Arduino and the ESP accordingly.
The result for an ESP-01 / ESP8266 with 8 Mbit flash:
The program finds the crystal frequency (CrystFreq) and flash size. In my case it keeps the SPI MODE set to QIO. Several tries flashing with SPI mode set to QIO failed, but an Internet search found that DOUT might be necessary to select manually.
Uncheck SpiAutoSet and select the appropriate SPI MODE, which for my ESP8266 was DOUT. SPI Mode seems to control the way the ESP flashes itself.
Then select the correct files to flash, according to the README.md file of the ESP firmware, and click START:
For baud rates, using an Arduino MKR with SAMD21 microcontroller, connected to the PC using native USB, I successfully have flashed with baud rates up to 1500000.
Reset the Arduino, which makes the Arduino program reset the ESP8266.
Open a serial monitor or terminal emulator like Putty. Make sure to send both NewLine and Carriage Return as line feeds. May manually be entered as Ctrl-M + Ctrl-J instead of using the ENTER key.
Run the AT+GMR command:
Firmware upgraded successfully!