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Fix I2C init hang when the SCL pin is pulled low.

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We added a check to make sure the pins are in a high state before
initing the bus. This leads to a friendly error message when someone
forgets to add the pull up resistors to their circuit.
This commit is contained in:
Scott Shawcroft 2018-03-26 15:13:52 -07:00
parent ea39f4378e
commit 37538fc0e7
1 changed files with 13 additions and 6 deletions
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19
ports/atmel-samd/common-hal/busio/I2C.c
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@ -72,6 +72,19 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
mp_raise_ValueError("Invalid pins");
}
// Test that the pins are in a high state. (Hopefully indicating they are pulled up.)
gpio_set_pin_function(sda->pin, GPIO_PIN_FUNCTION_OFF);
gpio_set_pin_function(scl->pin, GPIO_PIN_FUNCTION_OFF);
gpio_set_pin_direction(sda->pin, GPIO_DIRECTION_IN);
gpio_set_pin_direction(scl->pin, GPIO_DIRECTION_IN);
gpio_set_pin_pull_mode(sda->pin, GPIO_PULL_OFF);
gpio_set_pin_pull_mode(scl->pin, GPIO_PULL_OFF);
if (!gpio_get_pin_level(sda->pin) || !gpio_get_pin_level(scl->pin)) {
mp_raise_RuntimeError("SDA or SCL need a pull up");
}
gpio_set_pin_function(sda->pin, sda_pinmux);
gpio_set_pin_function(scl->pin, scl_pinmux);
// Set up I2C clocks on sercom.
samd_peripherals_sercom_clock_init(sercom, sercom_index);
@ -80,12 +93,6 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
mp_raise_OSError(MP_EIO);
}
gpio_set_pin_pull_mode(sda->pin, GPIO_PULL_OFF);
gpio_set_pin_function(sda->pin, sda_pinmux);
gpio_set_pin_pull_mode(scl->pin, GPIO_PULL_OFF);
gpio_set_pin_function(scl->pin, scl_pinmux);
// clkrate is always 0. baud_rate is in kHz.
// Frequency must be set before the I2C device is enabled.