[TW#26603] I2C master reset routine doesn't work #2494
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related to #680 |
Alvin1Zhang
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igrr
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Jan 24, 2019
… SDA closes #2494 closes #2493 closes #2496 1. Change bus reset to handle interrupted READ sequences. 2. Slow down I2C to 100khz during reset 3. If a SLAVE device was in a read operation when the bus was interrupted, the SLAVE device is controlling SDA.The only bit during the 9 clock cycles of a byte READ the MASTER(ESP32) is guaranteed control over, is during the ACK bit period. If the SLAVE is sending a stream of ZERO bytes, it will only release SDA during the ACK bit period. The master(ESP32) cannot generate a STOP unless SDA is HIGH. So, this reset code synchronizes the bit stream with, Either, the ACK bit, Or a 1 bit.
igrr
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Jan 29, 2019
… SDA closes #2494 closes #2493 closes #2496 1. Change bus reset to handle interrupted READ sequences. 2. Slow down I2C to 100khz during reset 3. If a SLAVE device was in a read operation when the bus was interrupted, the SLAVE device is controlling SDA.The only bit during the 9 clock cycles of a byte READ the MASTER(ESP32) is guaranteed control over, is during the ACK bit period. If the SLAVE is sending a stream of ZERO bytes, it will only release SDA during the ACK bit period. The master(ESP32) cannot generate a STOP unless SDA is HIGH. So, this reset code synchronizes the bit stream with, Either, the ACK bit, Or a 1 bit.
catalinio
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Jun 28, 2019
… SDA closes espressif/esp-idf#2494 closes espressif/esp-idf#2493 closes espressif/esp-idf#2496 1. Change bus reset to handle interrupted READ sequences. 2. Slow down I2C to 100khz during reset 3. If a SLAVE device was in a read operation when the bus was interrupted, the SLAVE device is controlling SDA.The only bit during the 9 clock cycles of a byte READ the MASTER(ESP32) is guaranteed control over, is during the ACK bit period. If the SLAVE is sending a stream of ZERO bytes, it will only release SDA during the ACK bit period. The master(ESP32) cannot generate a STOP unless SDA is HIGH. So, this reset code synchronizes the bit stream with, Either, the ACK bit, Or a 1 bit.
catalinio
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Jun 28, 2019
… SDA closes espressif/esp-idf#2494 closes espressif/esp-idf#2493 closes espressif/esp-idf#2496 1. Change bus reset to handle interrupted READ sequences. 2. Slow down I2C to 100khz during reset 3. If a SLAVE device was in a read operation when the bus was interrupted, the SLAVE device is controlling SDA.The only bit during the 9 clock cycles of a byte READ the MASTER(ESP32) is guaranteed control over, is during the ACK bit period. If the SLAVE is sending a stream of ZERO bytes, it will only release SDA during the ACK bit period. The master(ESP32) cannot generate a STOP unless SDA is HIGH. So, this reset code synchronizes the bit stream with, Either, the ACK bit, Or a 1 bit.
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Hi,
I have an I2C device which was causing a bus lockup (it contained some undocumented behaviour). However, this caused me to discover that the I2C master reset routine is incorrect. Please see #2493 for an explanation and details of the problem.
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