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I have a flight controller that has one uart to little. So i tried to remap SERIAL_TX 5 (That doesn't exitst on the FC) to pin A09, that previously had SERIAL_TX 1, but that doesn't seem to work. I also tried to remap SERIAL_TX 5 to LED_STRIP, but that didn't work either. Is there something else you have to do to get it working?

The commands I used was:

resource SERIAL_TX 1 NONE

resource SERIAL_TX 5 A09

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  • $\begingroup$ I think more information may be required as to what SERIAL_RX1 is connected to. Have you considered using soft-serial and configuring via resource remapping to SERIAL_TX11 which is soft-serial 1. $\endgroup$
    – Paul Kendall
    Apr 15, 2020 at 19:26
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    $\begingroup$ @PaulKendall absolutely this. I’d recommend adding this as an answer so it shows up for people searching $\endgroup$
    – Drones and Whatnot
    Apr 15, 2020 at 19:32
  • $\begingroup$ This question is specific only to existing betaflight functionality and should be asked on their forums. $\endgroup$
    – Kenn Sebesta
    Apr 15, 2020 at 20:22
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    $\begingroup$ I'd say it qualifies. Betaflight is used in drones after all. $\endgroup$
    – Hannes Hultergård
    Apr 15, 2020 at 20:37

1 Answer 1

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Serial ports are hardware based, and cannot be remapped. You can however remap software serial ports. Keep in mind not every pin supports softserial either, as an available hardware timer is required. Typically you can use:

  • UART TX & RX pins
  • PPM Input pins
  • LED pins
  • Motor PWM output pins

If you have one of those free, proceed.

  1. Enable softserial from the Betaflight Configurator "Configuration" tab, then click "Save and Reboot".
    enter image description here

  2. Go to the "CLI" tab and type "resource SERIAL_TX 11 A09", hit enter, then type "save" and hit enter.
    enter image description here

  3. Go to "Ports" tab and assign the feature you want to "SOFTSERIAL1".
    enter image description here

Keep in mind that software serial is limited in terms of how fast it communicate information and the load it puts on the CPU. If you have a very intensive low-latency connection, typically try to avoid use softserial. Softserial is best suited to things like VTX control (smart audio and tramp protocol, etc), GPS, and smart-port telemetry, where latency, speed, or loss of signal during flight isn't an issue. While it can be used for other more system critical links like RC control, I would generally recommend against it, though it is theoretically possible.

Sources:
https://oscarliang.com/betaflight-soft-serial/
http://www.multirotorguide.com/guide/guide-how-to-set-up-the-softserial-uart/

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  • $\begingroup$ Thank you! Soft serial might even work better then, since smartport is what I'm trying to connect $\endgroup$
    – Hannes Hultergård
    Apr 15, 2020 at 20:23
  • $\begingroup$ Yep, for smartport softserial is exactly the solution! Glad it helped! $\endgroup$
    – QuadMcFly
    Apr 15, 2020 at 20:52

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