diff options
Diffstat (limited to 'libraries/Wire/src/utility')
| -rw-r--r-- | libraries/Wire/src/utility/twi.c | 173 | ||||
| -rw-r--r-- | libraries/Wire/src/utility/twi.h | 6 |
2 files changed, 143 insertions, 36 deletions
diff --git a/libraries/Wire/src/utility/twi.c b/libraries/Wire/src/utility/twi.c index 1a35146..e8a41a2 100644 --- a/libraries/Wire/src/utility/twi.c +++ b/libraries/Wire/src/utility/twi.c @@ -17,6 +17,7 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts + Modified 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts */ #include <math.h> @@ -24,8 +25,9 @@ #include <inttypes.h> #include <avr/io.h> #include <avr/interrupt.h> +#include <util/delay.h> #include <compat/twi.h> -#include "Arduino.h" // for digitalWrite +#include "Arduino.h" // for digitalWrite and micros #ifndef cbi #define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit)) @@ -43,6 +45,16 @@ static volatile uint8_t twi_slarw; static volatile uint8_t twi_sendStop; // should the transaction end with a stop static volatile uint8_t twi_inRepStart; // in the middle of a repeated start +// twi_timeout_us > 0 prevents the code from getting stuck in various while loops here +// if twi_timeout_us == 0 then timeout checking is disabled (the previous Wire lib behavior) +// at some point in the future, the default twi_timeout_us value could become 25000 +// and twi_do_reset_on_timeout could become true +// to conform to the SMBus standard +// http://smbus.org/specs/SMBus_3_1_20180319.pdf +static volatile uint32_t twi_timeout_us = 0ul; +static volatile bool twi_timed_out_flag = false; // a timeout has been seen +static volatile bool twi_do_reset_on_timeout = false; // reset the TWI registers on timeout + static void (*twi_onSlaveTransmit)(void); static void (*twi_onSlaveReceive)(uint8_t*, int); @@ -154,8 +166,12 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen } // wait until twi is ready, become master receiver + uint32_t startMicros = micros(); while(TWI_READY != twi_state){ - continue; + if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) { + twi_handleTimeout(twi_do_reset_on_timeout); + return 0; + } } twi_state = TWI_MRX; twi_sendStop = sendStop; @@ -183,28 +199,38 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen // up. Also, don't enable the START interrupt. There may be one pending from the // repeated start that we sent ourselves, and that would really confuse things. twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR + startMicros = micros(); do { TWDR = twi_slarw; + if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) { + twi_handleTimeout(twi_do_reset_on_timeout); + return 0; + } } while(TWCR & _BV(TWWC)); TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START - } - else + } else { // send start condition TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA); + } // wait for read operation to complete + startMicros = micros(); while(TWI_MRX == twi_state){ - continue; + if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) { + twi_handleTimeout(twi_do_reset_on_timeout); + return 0; + } } - if (twi_masterBufferIndex < length) + if (twi_masterBufferIndex < length) { length = twi_masterBufferIndex; + } // copy twi buffer to data for(i = 0; i < length; ++i){ data[i] = twi_masterBuffer[i]; } - + return length; } @@ -222,6 +248,7 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen * 2 .. address send, NACK received * 3 .. data send, NACK received * 4 .. other twi error (lost bus arbitration, bus error, ..) + * 5 .. timeout */ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait, uint8_t sendStop) { @@ -233,8 +260,12 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait } // wait until twi is ready, become master transmitter + uint32_t startMicros = micros(); while(TWI_READY != twi_state){ - continue; + if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) { + twi_handleTimeout(twi_do_reset_on_timeout); + return (5); + } } twi_state = TWI_MTX; twi_sendStop = sendStop; @@ -265,18 +296,27 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait // up. Also, don't enable the START interrupt. There may be one pending from the // repeated start that we sent outselves, and that would really confuse things. twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR + startMicros = micros(); do { - TWDR = twi_slarw; + TWDR = twi_slarw; + if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) { + twi_handleTimeout(twi_do_reset_on_timeout); + return (5); + } } while(TWCR & _BV(TWWC)); TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START - } - else + } else { // send start condition TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE) | _BV(TWSTA); // enable INTs + } // wait for write operation to complete + startMicros = micros(); while(wait && (TWI_MTX == twi_state)){ - continue; + if((twi_timeout_us > 0ul) && ((micros() - startMicros) > twi_timeout_us)) { + twi_handleTimeout(twi_do_reset_on_timeout); + return (5); + } } if (twi_error == 0xFF) @@ -356,7 +396,7 @@ void twi_reply(uint8_t ack) if(ack){ TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT) | _BV(TWEA); }else{ - TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT); + TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT); } } @@ -373,8 +413,19 @@ void twi_stop(void) // wait for stop condition to be exectued on bus // TWINT is not set after a stop condition! + // We cannot use micros() from an ISR, so approximate the timeout with cycle-counted delays + const uint8_t us_per_loop = 8; + uint32_t counter = (twi_timeout_us + us_per_loop - 1)/us_per_loop; // Round up while(TWCR & _BV(TWSTO)){ - continue; + if(twi_timeout_us > 0ul){ + if (counter > 0ul){ + _delay_us(us_per_loop); + counter--; + } else { + twi_handleTimeout(twi_do_reset_on_timeout); + return; + } + } } // update twi state @@ -396,6 +447,59 @@ void twi_releaseBus(void) twi_state = TWI_READY; } +/* + * Function twi_setTimeoutInMicros + * Desc set a timeout for while loops that twi might get stuck in + * Input timeout value in microseconds (0 means never time out) + * Input reset_with_timeout: true causes timeout events to reset twi + * Output none + */ +void twi_setTimeoutInMicros(uint32_t timeout, bool reset_with_timeout){ + twi_timed_out_flag = false; + twi_timeout_us = timeout; + twi_do_reset_on_timeout = reset_with_timeout; +} + +/* + * Function twi_handleTimeout + * Desc this gets called whenever a while loop here has lasted longer than + * twi_timeout_us microseconds. always sets twi_timed_out_flag + * Input reset: true causes this function to reset the twi hardware interface + * Output none + */ +void twi_handleTimeout(bool reset){ + twi_timed_out_flag = true; + + if (reset) { + // remember bitrate and address settings + uint8_t previous_TWBR = TWBR; + uint8_t previous_TWAR = TWAR; + + // reset the interface + twi_disable(); + twi_init(); + + // reapply the previous register values + TWAR = previous_TWAR; + TWBR = previous_TWBR; + } +} + +/* + * Function twi_manageTimeoutFlag + * Desc returns true if twi has seen a timeout + * optionally clears the timeout flag + * Input clear_flag: true if we should reset the hardware + * Output none + */ +bool twi_manageTimeoutFlag(bool clear_flag){ + bool flag = twi_timed_out_flag; + if (clear_flag){ + twi_timed_out_flag = false; + } + return(flag); +} + ISR(TWI_vect) { switch(TW_STATUS){ @@ -416,16 +520,16 @@ ISR(TWI_vect) TWDR = twi_masterBuffer[twi_masterBufferIndex++]; twi_reply(1); }else{ - if (twi_sendStop) + if (twi_sendStop){ twi_stop(); - else { - twi_inRepStart = true; // we're gonna send the START - // don't enable the interrupt. We'll generate the start, but we - // avoid handling the interrupt until we're in the next transaction, - // at the point where we would normally issue the start. - TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; - twi_state = TWI_READY; - } + } else { + twi_inRepStart = true; // we're gonna send the START + // don't enable the interrupt. We'll generate the start, but we + // avoid handling the interrupt until we're in the next transaction, + // at the point where we would normally issue the start. + TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; + twi_state = TWI_READY; + } } break; case TW_MT_SLA_NACK: // address sent, nack received @@ -457,17 +561,17 @@ ISR(TWI_vect) case TW_MR_DATA_NACK: // data received, nack sent // put final byte into buffer twi_masterBuffer[twi_masterBufferIndex++] = TWDR; - if (twi_sendStop) - twi_stop(); - else { - twi_inRepStart = true; // we're gonna send the START - // don't enable the interrupt. We'll generate the start, but we - // avoid handling the interrupt until we're in the next transaction, - // at the point where we would normally issue the start. - TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; - twi_state = TWI_READY; - } - break; + if (twi_sendStop){ + twi_stop(); + } else { + twi_inRepStart = true; // we're gonna send the START + // don't enable the interrupt. We'll generate the start, but we + // avoid handling the interrupt until we're in the next transaction, + // at the point where we would normally issue the start. + TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; + twi_state = TWI_READY; + } + break; case TW_MR_SLA_NACK: // address sent, nack received twi_stop(); break; @@ -560,4 +664,3 @@ ISR(TWI_vect) break; } } - diff --git a/libraries/Wire/src/utility/twi.h b/libraries/Wire/src/utility/twi.h index d27325e..85b9837 100644 --- a/libraries/Wire/src/utility/twi.h +++ b/libraries/Wire/src/utility/twi.h @@ -15,6 +15,8 @@ You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + + Modified 2020 by Greyson Christoforo (grey@christoforo.net) to implement timeouts */ #ifndef twi_h @@ -50,6 +52,8 @@ void twi_reply(uint8_t); void twi_stop(void); void twi_releaseBus(void); + void twi_setTimeoutInMicros(uint32_t, bool); + void twi_handleTimeout(bool); + bool twi_manageTimeoutFlag(bool); #endif - |