UART ESP Code Flashing


Programming / Flashing UART Control

In order to ease programming, a simple two transistor circuit is added to our boards which when connected to a USB to UART module, allows the host computer to control the DTR = Reset, and RTS = Boot Mode.  This makes recompiling and flashing so much simpler.



This UART Cable will also power the SDK board from the UARTs 3V3.  Some boards may not function fully (such as the RMIS as it needs 3V3 and 5v), but at least you can program / flash / test your code.

Remember, if using the CWX SDK board, do NOT connect the 3V Lithium battery as well as the UART cable.


What is in the box

Our UART programming cable kit, includes the UART and a header cable.  This cable has two 6 pin headers.  You only need one 6 pin header connector, so the other should be cut off.  You could alternatively cut the cable in two and use it to make another cable assembly.



Our USB to UART module has both of these RTS and DTR connections.


UART Connections to the Developer Interface on our SDK Boards.




  • The 6 way cable looms that are provided may not follow the same colours as in the below photo examples.  Please check the connections carefully!
  • Do not plug the 6 way header into the CWX and into the UART.  These connections will NOT work and could damage the UART and/or the SDK board.


Cable connection examples

The below information shows the connections required.  Once the loom is created, it can be used for all our boards.


Cable Soldered into a complete loom


Connections UART end

Note that this photo shows the 5V pin intact.  As we only need the 3V3, you maybe best (but optionally), cut this off to prevent accidental shorts.


For speed, glue from heat gun has been added to protect and strengthen the connections.

If heat shrink available, then this would more ideal and make for a neater cable but either option is good in order to save accidental shorts and help protect the wires from breaking.


Marking the connector

To make it easier, and safer, to help remember which way the connector is plugged into the developer interface, it would be ideal to mark the cable to indicate the 3V3 positive or ground end.


Completed UART Cable Loom


Leave a Reply

This site uses User Verification plugin to reduce spam. See how your comment data is processed.