Timeout/overflow problems

i am having problems with the mission planner to apm side of the data link. amp to mission planner works fine. i have 3dr 433 radios
i get data from the apm but cannot send any. when i try to send waypoints (or anything else) i get an error timeout.
the radios are are talking to each other (solid green) and link quality is good (no packets lost)
i have looked at the radio data in initial set up and there is a very high value (thousands) against SRX which is serial receive overflow.
i have tried swapping radios about and checked wires to no improvement
i am connecting to a apm 2.6 hex (3.2.1) with mission planner (1.3.24)
i have up dated the radio software to 1.9 and the apm is at the latest version.

any help greatly appreciated

Did you upgrade the firmware on both radios?

If you swap the radios does the problem change. Is the Rx and Tx connected on the APM side?


Hi Mike,

yes, both radios at 1.9

tried swapping the radios and no change.

not sure what the last question means. i am connected to the apm with the standard 5 pin to 6 pin cable. i have checked this with a multi meter.

i have also checked the 3.3v regulator. solid at 3.26v