I have several IO operation that I carry out on class init but they often fail with IOError. What I would like to do is delay a few hundred ms and try again until success or some defined timeout. How can I make sure each individual command succeeds before continuing/ending the loop? I assume there is a better way than an if statement for each item and a counter to check if all commands succeeded.
My current code below often fails with IOError and hangs the rest of the application.
def __init__(self):
print("Pressure init.")
self.readCoefficients()
def readCoefficients(self):
global a0_MSB;
global a0_LSB;
global b1_MSB;
global b1_LSB;
global b2_MSB;
global b2_LSB;
global c12_MSB;
global c12_LSB;
a0_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_A0_COEFF_MSB+0);
a0_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_A0_COEFF_LSB+0);
b1_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B1_COEFF_MSB+0);
b1_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B1_COEFF_LSB+0);
b2_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B2_COEFF_MSB+0);
b2_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B2_COEFF_LSB+0);
c12_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_C12_COEFF_MSB+0);
c12_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_C12_COEFF_LSB+0);
If it's OK for you that all the files are read one after the other, you can use a simple function.
import time
# ...
def readCoefficients(self):
global a0_MSB;
global a0_LSB;
global b1_MSB;
global b1_LSB;
global b2_MSB;
global b2_LSB;
global c12_MSB;
global c12_LSB;
max_retries = 15
a0_MSB = self.readretry(Pressure.MPL115A2_REGISTER_A0_COEFF_MSB+0, max_retries)
a0_LSB = self.readretry(Pressure.MPL115A2_REGISTER_A0_COEFF_LSB+0, max_retries)
b1_MSB = self.readretry(Pressure.MPL115A2_REGISTER_B1_COEFF_MSB+0, max_retries)
b1_LSB = self.readretry(Pressure.MPL115A2_REGISTER_B1_COEFF_LSB+0, max_retries)
b2_MSB = self.readretry(Pressure.MPL115A2_REGISTER_B2_COEFF_MSB+0, max_retries)
b2_LSB = self.readretry(Pressure.MPL115A2_REGISTER_B2_COEFF_LSB+0, max_retries)
c12_MSB = self.readretry(Pressure.MPL115A2_REGISTER_C12_COEFF_MSB+0, max_retries)
c12_LSB = self.readretry(Pressure.MPL115A2_REGISTER_C12_COEFF_LSB+0, max_retries)
def readretry(self, address, max_retries):
for i in range(max_retries):
try:
return Pressure.bus.read_byte_data(
Pressure.MPL115A2_ADDRESS,
address
)
except IOError as e:
# print(e)
time.sleep(0.1)
else:
raise IOError("Reading failed after multiple tries")
Note: You should not use globals, most specially in classes.