youen/OneWireArduinoSlave
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Add some comments about race condition

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destroyedlolo 2018-03-24 13:58:27 +01:00
parent 28f9205701
commit 08991060da
1 changed files with 4 additions and 0 deletions
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examples/DS18B20_DHT22/DS18B20_DHT22.ino
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@ -55,6 +55,7 @@ void owRcv( OneWireSlave::ReceiveEvent evt, byte cmd ){
case OW_Cmd::START_CONVERSION: case OW_Cmd::START_CONVERSION:
state = DeviceState::CONVERTING; state = DeviceState::CONVERTING;
OWSlave.beginWriteBit(0, true); // send zeros as long as the conversion is not finished OWSlave.beginWriteBit(0, true); // send zeros as long as the conversion is not finished
// consequently, we don't have to take care of race condition as no other command can arrive
break; break;
case OW_Cmd::READ_SCRATCHPAD: case OW_Cmd::READ_SCRATCHPAD:
state = DeviceState::WAIT4RESET; state = DeviceState::WAIT4RESET;
@ -72,6 +73,9 @@ void owRcv( OneWireSlave::ReceiveEvent evt, byte cmd ){
void setTemperature( float temp ){ // Write given temperature to the scratchpad void setTemperature( float temp ){ // Write given temperature to the scratchpad
int16_t raw = (int16_t)(temp * 16.0f + 0.5f); int16_t raw = (int16_t)(temp * 16.0f + 0.5f);
// We don't care about race condition as well as only one command
// can be processed at a time otherwise we are failing in error/collision
// condition.
scratchpad[0] = (byte)raw; scratchpad[0] = (byte)raw;
scratchpad[1] = (byte)(raw >> 8); scratchpad[1] = (byte)(raw >> 8);
scratchpad[8] = OWSlave.crc8((const byte*)scratchpad, 8); scratchpad[8] = OWSlave.crc8((const byte*)scratchpad, 8);