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TWI slave on ATmega644: clock stretching does not work
Quote:This makes me still think that it would work if only I could make the TWI Hardware hold the SCL line low until the ISR sets the TWINT flag (as described in the data sheet)....
Tuesday, 22 April 2008 - 09:44
TWI slave on ATmega644: clock stretching does not work
Hi, I can confirm the clock frequency is 8MHz, external clocking. CKSEL is set to "Ext. Clock; Start-up time: 6 CK + 0 ms", CKDIV = 0. The external frequency is 8MHz. But again, I...
Tuesday, 22 April 2008 - 09:31
TWI slave on ATmega644: clock stretching does not work
Yes, I saw this. We run the ATmega644 at 8MHz, so in theory I should be able to run the I2C bus up to 500KHz.
Monday, 21 April 2008 - 18:27
TWI slave on ATmega644: clock stretching does not work
I'm afraid the Write Collision was a Red Herring: it gets set in my initialisation: TWDR = 0xFF; TWCR = TWCR_ENABLE | TWCR_TWINT; Now I initialise the HW like this: TWAR...
Monday, 21 April 2008 - 18:25
TWI slave on ATmega644: clock stretching does not work
TWBR = 0 Prescaler = 0 (i.e. 1) I did not set those values, because the ATmega644 is always slave on the bus. Am I wrong?
Monday, 21 April 2008 - 18:16
TWI slave on ATmega644: clock stretching does not work
Thanks for the reply, The (external) pull-ups are 2.2kOhm, the cable is about 5cm long. The flanks of SCL and SDA are very steep (vertical on a screen with 100us/div), which makes...
Monday, 21 April 2008 - 18:08

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