How to save an UART port on your MSP protocol compatible Flight Controller for SmartPort telemetry (Part 2)

In part 1 I already made all the hardware modifications required, in this part I'll concentrate in programming and configuring the MSP to SmartPort Nano board.

The easiest way is to connect your FTDI or similar cable to MinimOSD (like you do when changing MWOSD configuration).

If ICSP wires were NOT soldered, then remember to put a jumper between RESET pin and GND, this way MinimOSD's Atmega will be disabled and will not interfere with Nano programming.

Download the MSP to SmartPort Arduino sketch. Edit code to fit your needs. You must modify config.h file to disable ISP programmer if ICSP wires were NOT soldered (just comment line #define ISP_MODE with // in front of it) to avoid ISP mode and enter into MSP to SmartPort mode immediately.

I'm using a custom LUA script on my Taranis, so this MSP to Smartport code is adapted to my script, but you can disable this, commenting line #define CFTS_ENABLED in config.h.

If you wish to use also the CFTS script, please check this post. Here you are a mini video of the script (this is a video of an old work in progress version, but you'll get the idea):

To upload the sketch, you may need to press the reset button on the Nano board as soon as the Uploading word appears on the Arduino GUI to be able to upload the sketch, if your board doesn't feature the autoreset function.

After Nano being programmed, remove reset jumper from MinimOSD (if you put it before).

Now you should have the MSP to SmartPort converter working. If ICSP wires were soldered, you should have also an ISP programmer for the MinimOSD.

Wire all. Double check connections before applying power.

Powering up the board

If ICSP wires were soldered, when power is applied to the MinimOSD, the Nano board will enter in ISP programming mode for 5 seconds (you can change period on the sketch, check config.h file), after that, if no data is sent to the Nano board, will enter in MSP to Smartport mode and MWOSD will start running normally. You should receive telemetry data on the transmitter.

If ICSP wires were NOT soldered, MWOSD will start as soon as power is applied. You must modify config.h file to disable ISP programmer (just comment line #define ISP_MODE with // in front of it) to avoid ISP mode and enter into MSP to SmartPort mode immediately.

If you need to program or update MinimOSD firmware, check this post for information of how to program via ISP using avrdude. As I said before, you can use this method to update MWOSD firmware if you soldered the ICSP wires, as explained in part 1.

Finally some credits. The MSP to SmartPort sketch has taken a lot of code from MWOSD and uses FrSkySport library for SmartPort handling, this library for software serial and a modified version of the Arduino ISP module for ISP programming.

Hope it's useful for you as it's for me. See you soon!