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i2c.c: recover from error conditions. 

This is
- clearing 'i2c_should_end', so i2c_write() doesn't hang and
- draining the buffer on errors.

This way we loose the remaining transmission, which is typically
half a character, but we no longer stall the entire firmware main
loop.

Actually, such error conditions are surprisingly frequent, at
least on the test hardware. Now they result in some flickering
of the displayed numbers.
This commit is contained in:
Markus Hitter 2016-04-25 21:57:54 +02:00
parent dcc970d2fd
commit ea2a10fa76
1 changed files with 16 additions and 0 deletions
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16
i2c.c
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@ -213,6 +213,16 @@ void i2c_write(uint8_t data, uint8_t last_byte) {
delay_us(10);
}
// Recover from error conditions by draining the buffer.
if ((i2c_state & I2C_ERROR_BUS_FAIL) ||
(i2c_state & I2C_ERROR_NO_ANSWER) ||
(i2c_state & I2C_ERROR_NACK)) {
while (buf_canread(send)) {
buf_pop(send, TWDR);
}
i2c_state = I2C_MODE_FREE;
}
if (i2c_state & I2C_MODE_FREE) {
// No transmission ongoing, start one.
i2c_state = I2C_MODE_SAWP;
@ -274,6 +284,8 @@ ISR(TWI_vect) {
serial_writechar('1');
#endif
i2c_state |= I2C_ERROR_BUS_FAIL;
// Let i2c_write() continue.
i2c_should_end = 0;
// Send stop condition.
TWCR = (1<<TWINT)|(I2C_MODE<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|(1<<TWEN)|(0<<TWIE);
break;
@ -325,6 +337,8 @@ ISR(TWI_vect) {
serial_writechar('5');
#endif
i2c_state |= I2C_ERROR_NO_ANSWER;
// Let i2c_write() continue.
i2c_should_end = 0;
// Send stop condition.
TWCR = (1<<TWINT)|(I2C_MODE<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|(1<<TWEN)|(0<<TWIE);
break;
@ -368,6 +382,8 @@ ISR(TWI_vect) {
serial_writechar('7');
#endif
i2c_state |= I2C_ERROR_NACK;
// Let i2c_write() continue.
i2c_should_end = 0;
// Send stop condition.
TWCR = (1<<TWINT)|(I2C_MODE<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|(1<<TWEN)|(0<<TWIE);
break;