Hi all!This isn't a discussion about wireless telemetry but more to do with the telemetry port itself.Could somewone tell me what the signal voltage levels are on the tlemetry port on the Ardupilot Mega.I hoping to test my telemetry link by using a serial to USB adapter, but when I do I get a garbled mess of data in my "raw data" window. I have no problems when I defie the GCS port as the USB port and send the data that way (I get the normal MAVLINK data stream)I have checked baud rates both ends and have got tx/rx and ground all correct.I have double checked by forcing GCS to telem port correct protocols etc.Is the APM designed to output at normal RS-232 signal level voltages or is it TTL.If it is TTL, I have 2 questions...1. Is logic 1 and logic 0 reversed when using TTL (compared to serial RS-232)2. Is it likely that I have fried my Ardupilot mega telemetry using a USB to serial adapter. (I assume that usb to serial uses +5V to -5V on the serial side?)Any help yould be greatly appreciated as next step is to attach the Digi Xtend modems!Many thanks,John Cousins
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Logic 0 and logic 1 are the same as RS232 however the voltages are the other way round. +12V<-->0V and -12V<-->5V. Hardly anyone uses the 12V signals (although these are the real RS232 ones) for small short range serial any more.
2) Not very likely no.
There is a serial test sketch in the source code. You could try that. It is easier to know with that if the garbled garbage is MAVLink or if it is data gone silly in transmission - because it uses no MAVLink.
Replies
Hi,
APM uses 5V TTL logic.
Logic 0 and logic 1 are the same as RS232 however the voltages are the other way round. +12V<-->0V and -12V<-->5V. Hardly anyone uses the 12V signals (although these are the real RS232 ones) for small short range serial any more.
2) Not very likely no.
There is a serial test sketch in the source code. You could try that. It is easier to know with that if the garbled garbage is MAVLink or if it is data gone silly in transmission - because it uses no MAVLink.
Regards
Soren
I have been connecting my APM2.5 directly to the Rpi with no issues. 5 <> 3.3 volt is no problem :)
Hi
Did you find out about the TTL level ? :)