update API between DonkeyCar and MM1

[mockbot]

Hello again,

the current API between DonkeyCar and MM1 is too weak to support all fantasitic MM1 features.
Why not using a similar API like GYM part and remote DCsimulator ?
Instead of exchanging throttle and steering only, exchange simple JSON data in both directions.
The API may be extended very easy to support additional features of MM1.

PoC exchange json :: https://github.com/mockbot/SerialJsonGW/blob/master/MM1JsonAgent.py

TODO: more reliable serial communication in both directions.

[wallarug]

Hi @mockbot

The Donkey Car Environment doesn't currently support JSON transfers between any parts. It would not be standard and would require a lot of extra work.

How did you go with testing the Pymata things? That would be easier to integrate, but not immediately.

I am currently waiting for the Donkey Car Maintainers to push through a big Pull Request before making any more changes to the Robo HAT parts.

[mockbot]

I like pymata_rh very much, but it has too many dependencies from other developers and ideas.

[mockbot]

this is the key part of action :-)
if(len(datastr) >= 10):
steering_val = steering.value
throttle_val = throttle.value
try:
steering_val = int(datastr[:4])
throttle_val = int(datastr[-4:])

this must be replaced by simple json encode/decode feature... at micropython and mm1-part

while True:
json_string = sio.readline()
try:
data = json.loads(json_string)
if enable_stdio == 1:
print(data["serial"],data["gyro"],data["accel"],data["magnetic"],data["temperature"],data["vshunt"],data["vbus"],data["current"],data["nmea"])
except:
print("ERROR:"+str(err)+" json decode error !!!")
err=err+1