Using AC3.5 RC8, I keep finding FLOW_ENABLE resetting back to zero.
If the PX4FLOW board is already running when the Pixhawk boots up it works fine, however if they are both powered on at the same time, FLOW_ENABLE is reset to 0
I can reproduce this easily:
1) Power copter from flight battery
2) Connect MP via 3DR radio
3) Set FLOW_ENABLE to 1
4) Reboot Pixhawk (using reboot button from Misson Planner CTRL+F menu)
5) Check opt_m_x and opt_m_y are showing non-zero values.
6) Reboot pixhwawk again (using reboot button from MP)
7) Check FLOW_ENABLE = 1 and opt_m_x and opt_m_y are still showing non-zero values.
8) Disconnect flight battery for 10s
9) Connect flight battery
10) See FLOW_ENABLE is now back to 0 in MP.
I have tried this with the PX4FLOW powered from both i2c power, and have just rewired it to get power from the 2nd BEC on the servo rail (measured clean 5v), so this is not a voltage sag issue.
To be sure, I've reflashed the correct KLT flow firmware from the link on the Copter docs.
This was working perfectly in AC3.4.6
Seems similar issues have already been reported elsewhere: