I have two Arduino Megas with HC-05 on Serial1 connected to a Raspberry Pi 3b+ via bluetooth, using the HC-05 and the RPi's built-in bluetooth, and python's
pySerialTransfer library to make the connections.
For reasons I am still trying to root cause, the bluetooth connection gets severed a few times an hour. Ideally, I'd get hours to perhaps a day between severed connections; is this a realistic goal?
Over a course of a few days, my testing has shown:
- Mega#1 median connection duration is 10 minutes & 88 minute max duration; 25 bytes sent by RPi->Arduino, and by Arduino->RPi every 0.2sec
- Mega#2 median connection duration is 38 minutes & 153 minute max duration; 4 bytes sent by RPi->Arduino, and by Arduino->RPi every 0.2sec
During this testing, they're completely stationary within about 12" of each other, so range should not be an issue.
My RPi code detects a lost connection by virtue of failure to receive a message within 5 seconds, and attempts to reestablish the connection, and that is successful about 80% of the time. I have a second-tier of lost-connection recovery - resetting the HC-05 via an Arduino-triggered MOSFET - if a message isn't received by the Arduino in ~20 seconds, that works in the remainder of the cases, so I'm ultimately able to systematically recover within a max of about 30 seconds. However, this lost connection for ~10-30 seconds every 10-60 minutes causes a poor user experience for my remote controls.
The Python errors given for about 95% of the failures are a lack of a receipt of a heartbeat message from the Arduino to the RPi python; about 5% give a unspecific
[Errno 5] Input/output error error.
While I'm running down multiple theories via day-long stability tests (longer byte transmissions are more error prone? there's some bug in my Arduino code causing crashes, so remove all logic except the send/receive code to test?), I've read a few posts about how finicky & fragile bluetooth can be, and so I'm curious for some thoughts about the general goal / attempt to get a longer-term (hours to a day or more) connection.
Have folks been able to achieve this with the HC-05 on Arduino? Or is a dropped connection every 10-60 minutes just something one needs to deal with through robust code? Thank you.