diff options
| -rw-r--r-- | extmod/machine_i2c.c | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/extmod/machine_i2c.c b/extmod/machine_i2c.c index ceddf0730e..f7d2380245 100644 --- a/extmod/machine_i2c.c +++ b/extmod/machine_i2c.c @@ -34,6 +34,9 @@ #if MICROPY_PY_MACHINE_I2C +// Clock stretching limit, so that we don't get stuck. +#define I2C_STRETCH_LIMIT 255 + typedef struct _machine_i2c_obj_t { mp_obj_base_t base; uint32_t us_delay; @@ -53,6 +56,11 @@ STATIC void mp_hal_i2c_scl_low(machine_i2c_obj_t *self) { STATIC void mp_hal_i2c_scl_release(machine_i2c_obj_t *self) { mp_hal_pin_od_high(self->scl); + mp_hal_i2c_delay(self); + // For clock stretching, wait for the SCL pin to be released, with timeout. + for (int count = I2C_STRETCH_LIMIT; mp_hal_pin_read(self->scl) == 0 && count; --count) { + mp_hal_delay_us_fast(1); + } } STATIC void mp_hal_i2c_sda_low(machine_i2c_obj_t *self) { @@ -71,7 +79,6 @@ STATIC void mp_hal_i2c_start(machine_i2c_obj_t *self) { mp_hal_i2c_sda_release(self); mp_hal_i2c_delay(self); mp_hal_i2c_scl_release(self); - mp_hal_i2c_delay(self); mp_hal_i2c_sda_low(self); mp_hal_i2c_delay(self); } @@ -81,7 +88,6 @@ STATIC void mp_hal_i2c_stop(machine_i2c_obj_t *self) { mp_hal_i2c_sda_low(self); mp_hal_i2c_delay(self); mp_hal_i2c_scl_release(self); - mp_hal_i2c_delay(self); mp_hal_i2c_sda_release(self); mp_hal_i2c_delay(self); } @@ -108,14 +114,12 @@ STATIC int mp_hal_i2c_write_byte(machine_i2c_obj_t *self, uint8_t val) { } mp_hal_i2c_delay(self); mp_hal_i2c_scl_release(self); - mp_hal_i2c_delay(self); mp_hal_i2c_scl_low(self); } mp_hal_i2c_sda_release(self); mp_hal_i2c_delay(self); mp_hal_i2c_scl_release(self); - mp_hal_i2c_delay(self); int ret = mp_hal_i2c_sda_read(self); mp_hal_i2c_delay(self); @@ -150,7 +154,6 @@ STATIC int mp_hal_i2c_read_byte(machine_i2c_obj_t *self, uint8_t *val, int nack) uint8_t data = 0; for (int i = 7; i >= 0; i--) { mp_hal_i2c_scl_release(self); - mp_hal_i2c_delay(self); data = (data << 1) | mp_hal_i2c_sda_read(self); mp_hal_i2c_scl_low(self); mp_hal_i2c_delay(self); @@ -163,7 +166,6 @@ STATIC int mp_hal_i2c_read_byte(machine_i2c_obj_t *self, uint8_t *val, int nack) } mp_hal_i2c_delay(self); mp_hal_i2c_scl_release(self); - mp_hal_i2c_delay(self); mp_hal_i2c_scl_low(self); mp_hal_i2c_sda_release(self); |