I try to steer a drone with a joytick from pc over WiFi. On board I have an Aruino like board called Particle Photon. I want to send 3 floats (pitch, roll, throttle) via TCP and I contocted this sort of thing:
On the PC - python - client side of things, it just sends this with 20 FPS/50ms frequency:
try:
s.sendall(bytearray(struct.pack("f", float(-20*axis0))))
s.sendall(bytearray(struct.pack("f", float(20*axis1))))
s.sendall(bytearray(struct.pack("f", float(axis2))))
except socket.error as e:
print("error while sending :: " + str(e))
where s is my socket.
On the server-drone side I have this:
if (myIMU.delt_t >= 25)
{
if (TCPcomms && client.connected()){
// Check for 12 bytes (3 floats) from joystick input --
// if we have them, update roll, pitch and throttle references
if(client.available() >= 12){
byte tempBuff[4];
float newInput[3];
for(int j = 0; j < 3; j++){
for(int i = 0; i < 4; i++)
{
tempBuff[i] = client.read();
}
newInput[j] = *((float*)(tempBuff));
}
roll_reference = newInput[0];
pitch_reference = newInput[1];
throttle_reference = newInput[2];
...
Drone loop works a lot faster hence the time check at the top (no need to check too often). Now, I print-debugged it on slower speeds and everything seems fine. Whenever there are 3 floats ready, drone code reads them, if not it just continues.
But half the times I try to run it with normal speeds Particle board just checks out after some time and disconnects entirely. Apparently it does that whenever there is any problem, but it doesn't make a good job of communiocating what it is...
Earlier I also had a mechanism that disconnects after X seconds but it also dropepd connections often. I checked with Wireshark that it always coincided with retransmitting packets.
I guess my question is is it WiFi/TCP's fault and it's just not good for this type of a task or am I doing something stupid? Did anyone have a simillar issue with Arduino or Particle?
