I had hoped to be able to use a 433MHz module by Low Power Radio Solutions as my link between the HKGCS and my Ardupilot Mega. Initially the modules seemed to work well but when I tried it with version 2.012 the link was very unreliable. I am running at only 19200baud. I also noticed some unknown message errors.
I connected the serial port 3 on the APM direct to my laptop and of course it works fine but I did notice one thing and that was the length of the data packets - up to 109 two byte characters or 218characters. This was the likely cause of my problem as the buffer in the LPRS module is only 180characters and it requires some time after the last character to transmit the data and before being able to receive new data.
I checked the spec on the Xbee pro module - I am using 2.4Ghz for video and the 868Mhz band here in the UK has a 10% duty cycle limit - and that has a 202 character buffer so that may also give problems.
Now I am no expert on serial comms but what I have found sort of makes sense and may explain why others are not getting rock solid comms.
Anyone got any suggestions?
Peter
Replies
The LPRS module has only a data buffer and requires time to empty it whilst it transmits the data. This is a significant limit to achieving high continuous throughput.
The Xbee has a data buffer and a transmit buffer and can achieve very good throughput rates as a result unless you use the 868Mhz European versions.
Peter