(1) ATmega168
(1) TC74 - Digital Temperature sensor.
Using the 2-wire module within the ATMega168 here is my code, straight out of the datasheet:
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Code: Select all
// talk to temp sensor. prep to send the temp back.
TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); // send a start condition
while (!(TWCR & (1<<TWINT))); // Wait for "start sent"
TWDR = (sensor_address <<1); // Sensor Address, Write
TWCR = (1<<TWINT) | (1<<TWEN); // Start transfer. Send TWDR out.
while (!(TWCR & (1<<TWINT))); // Wait for "TWDR sent"
printf("TWSR should be 0x18 - %x \n", (TWSR & 0xF8)); // THIS CHECKS OUT OK !!!
TWDR = 0x00; // Address "temperature reading" byte
TWCR = (1<<TWINT) | (1<<TWEN); // Start transfer. Send 0x00.
while (!(TWCR & (1<<TWINT))); // wait for "Data sent"
printf("TWSR should be 0x28 - %x \n", (TWSR & 0xF8)); // THIS PRINTS '40' every time !!!!
I have found that I can't manage to get the correct TWSR code (0x28) after sending the "0x00" byte - I get the code 0x40; meaning " Slave+R sent, ACK received". I get the correct codes for all other 2-wire exchanges with the temperature sensor.
In the end, the TWSR code for the exchange in question doesn't seem to matter - I am still able to read the temperature byte correctly!
The reason for my desire to get the TWSR code correct is that my next venture is to try a wii nunchuck that I have... It is not going so well & I get the same TWSR errors at the exact same point in the conversation.
Thanks,
