Stm32F407 UART question

[Bogdan]

Posted on April 24, 2016 at 07:10

Hello all,

i have a stm32F407VG setup which comunicates telemetry data over a RC receiver from FRSKY, which uses a ''inverted serial protocol''. I am wondering if its posible to invert polarity of the output from 32f4 without aditional hardware, only software based.

[mark239955_stm1]

Posted on April 25, 2016 at 02:44

The short answer to your question is, no, it's not possible to invert the output of the UART's on an STM32F4.  It is possible to write a ''soft'' UART, or if you know what you're doing you can configure timer/s and DMA, or SPI and DMA, to behave like a UART; any of those could be inverted.

The more important question for you in the short term though is, what signalling levels does your RC system use?  If it's inverted, chances are that it uses RS232 (nominally +/-12V) signalling, for which you require a level shifter IC.  It may be using TTL levels, but are they 5V or 3.3V (or something else)?  Failure to match signalling voltages may cause smoke to issue from one or more parts of your system.