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I can confirm that the ETRX357USB-LRS+8M can be flashed with an appropriate EZSP firmware without the use of any programming hardware. So, without any guarantees (you might -but probably won’t- brick your device), here’s how:

  1. Download the firmware. I used some random blob someone put on github that at least seemed to have the right name. What could possibly go wrong, right?
  2. (Install USB-to-serial drivers for the device. Linux will load the driver automatically when you plug in; not sure about other OSes.)
  3. Install a serial port communication app that supports X-MODEM. (debian/ubuntu: sudo apt-get install minicom, installs lrzsz, too) Run it and configure it (sudo minicom -s) to use the fake serial port (/dev/ttyUSB0) at 19200 baud 8N1. Disable both hardware (RTS/CTS) and software (XON/XOFF) flow control.
    • Connect USB stick
    • ls -l /dev/ttyUSB* -> note the number
      • Usually should be /dev/ttyUSB0.
    • wget '' -O 'em357-ncp-uart-xon-xoff-use-with-serial-uart-bl-500.ebl'
    • sudo apt-get install minicom
    • sudo minicom -s
    • Serial port setup
    • A (Serial Device: /dev/model)
    • Type /dev/ttyUSB0
    • Enter to accept.
    • E (Bps/Par/Bits: 115200 8N1)
    • B × 3 (Current: 19200 8N1)
    • Enter to return.
    • F (Hardware Flow Control: Yes -> change to No)
    • // G (Software Flow Control: No -> keep at No)
    • Enter to go to main menu.
    • Exit to go to interactive telnet like session.
    • To exit minicom, use CTRL-A, then Q.
  4. Type AT , you should get OK in response. Now type AT+BLOAD . The device will reboot into the bootloader.
  5. Change the baud rate in the serial port communication app setting to 115200 baud. (exit minicom using CTRL-A Q, run sudo minicom -s again)
  6. Pressing enter in the terminal should now show you a three-option boot loader menu. Choose option 1.
  7. C characters will start showing. Don’t wait for this to finish, but start an X-MODEM upload of the firmware you downloaded earlier (use CTRL-A, then S in minicom). You have 60 seconds to start the upload.
  8. After the upload finished, you should return to the menu. Now select option 2, to reboot into the new firmware. You’re done. Enjoy!


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