How do you upgrade RN4020 firmware on a customer board?

1

To be able to upgrade the firmware on the RN4020, you need access to the following pins on RN4020:

  1. RX
  2. TX
  3. GND
  4. CTS
  5. RTS
  6. VCC (Optional if the RN4020 can be powered externally)
  7. WAKE _SW
  8. CMD/MLDP
​

If you have a microcontroller on the board, please make sure it does not interfere with the UART pins. If it is pre-programmed, you can hold it in reset until the upgrade is complete.
You also need to have a USB to UART bridge. We recommend the MCP2221 Breakout Module.

2

Make the following connections:

  • RN4020 > USB to UART bridge
  • RX > TX
  • TX > RX
  • CTS > RTS
  • RTS > CTS
  • GND > GND
  • VCC > VCC
  • WAKE_SW > VCC
  • CMD/MLDP > GND

3

Once the correct connections are made, open up a terminal and connect to the RN4020 through the USB to UART bridge you made the connection to. Select the right COM port with 115200 Bd, 8-bit, one stop, no parity and hardware flow control enabled.

4

Power cycle the RN4020 and it will print CMD on the terminal. Send the following commands to the module:
SF,1
R,1
SR,820000000
R,1

5

Send D and make sure the flow control is on by checking features.

6

Once confirmed, download the RN4020 DFU utility from the RN4020 landing page (under Documents > Software).

7

Close your terminal, open DFU utility and select right COM port, select the firmware you want to be flashed on RN4020 and click Update.

​

Do not disconnect the RN4020 while it is upgrading, this may brick RN4020.

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