AVR Error Handling: I2C, SPI etc

avri2ctwi

How would one go about handling errors in AVR interfaces that do not specifically provide any acknowledgement scheme?

For example, I have an I2C temperature sensor which I poll every 1 hour. So every hour my AVR sends a TWI start condition to the sensor and gets the temperature at the end of it.Now
tet's say for some reason the sensor does not respond. Maybe it's been taken out, burned out etc.
So how can I check for such in my code and inform the user?

Right now I am using the polling method. Infinite loop till TWINT is set in the TWCR register

while ((TWCR & (1<<TWINT)) == 0){};
return TWDR;

Best Answer

The I2C module provides a way to identify erros, once you send, let's say a START condition or whatever you have to verify the TWSR register (TWI Status register) and it should match the state you are expecting (e.g. Aknowledge from slave). There is a flow diagram for each working mode showcasing the different status values.

Related Solutions

Electronic – SMBus with AVR

The SMBus protocol is usable with AVR microcontrollers, either by bit-banging the protocol, or through the I2C hardware support. Some SMBus devices apparently have had problems with the I2C protocol as implemented in earlier versions of the Arduino "wire.h" libraries, but since the question does not mention an Arduino, presumably that is not part of the problem. @vicatcu points out that this issue has been resulved in the current Arduino release.

See Peter Fleury's I2C Master Interface library for AVR-gcc as a starting point. This works with a couple of SMBus sensors I use.

Also, there are a couple of discussions on SMBus implementation at the AVR Freaks forum, that might help you navigate around specific pot-holes encountered along the SMBus road.

Electronic – AVR TWI (I2C) problem

The problem is at

TWCR |= (1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI

As per Atmel datasheets, the flags you set in TWCR "must be cleared by software when [what you're trying to send] has been transmitted."

So don't "or" TWCR with your flags but write all the flags in the register to their appropriate values, like

TWCR = (1<<TWINT)|(1<<TWEN);    // Clear TWI interrupt flag,Enable TWI

Best Answer

Related Solutions

Electronic – SMBus with AVR

Electronic – AVR TWI (I2C) problem

Related Topic