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I2CManager - support slower I2C speeds.

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Previously the driver allowed speeds down to 32kHz but lower speeds were not implemented correctly.
This commit is contained in:
Neil McKechnie 2021-10-08 13:28:43 +01:00
parent 6dde811279
commit 80472a76dc
2 changed files with 15 additions and 4 deletions
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6
I2CManager.cpp
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@ -179,7 +179,7 @@ I2CManagerClass I2CManager = I2CManagerClass();
/***************************************************************************
* Block waiting for request block to complete, and return completion status.
* Since such a loop could potentially last for ever if the RB status doesn't
* change, we set a high limit (0.1sec, 100ms) on the wait time and, if it
* change, we set a high limit (1sec, 1000ms) on the wait time and, if it
* hasn't changed by that time we assume it's not going to, and just return
* a timeout status. This means that CS will not lock up.
***************************************************************************/
@ -187,8 +187,8 @@ uint8_t I2CRB::wait() {
unsigned long waitStart = millis();
do {
I2CManager.loop();
// Rather than looping indefinitely, let's set a very high timeout (100ms).
if ((millis() - waitStart) > 100UL) {
// Rather than looping indefinitely, let's set a very high timeout (1s).
if ((millis() - waitStart) > 1000UL) {
DIAG(F("I2C TIMEOUT I2C:x%x I2CRB:x%x"), i2cAddress, this);
status = I2C_STATUS_TIMEOUT;
// Note that, although the timeout is posted, the request may yet complete.

13
I2CManager_AVR.h
View File

@ -62,7 +62,18 @@
* Set I2C clock speed register.
***************************************************************************/
void I2CManagerClass::I2C_setClock(unsigned long i2cClockSpeed) {
TWBR = ((F_CPU / i2cClockSpeed) - 16) / 2;
unsigned long temp = ((F_CPU / i2cClockSpeed) - 16) / 2;
for (uint8_t preScaler = 0; preScaler<=3; preScaler++) {
if (temp <= 255) {
TWBR = temp;
TWSR = (TWSR & 0xfc) | preScaler;
return;
} else
temp /= 4;
}
// Set slowest speed ~= 500 bits/sec
TWBR = 255;
TWSR |= 0x03;
}
/***************************************************************************