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Check for floating pins by pulling them low briefly before testing their values.

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This commit is contained in:
Scott Shawcroft 2018-03-26 16:32:16 -07:00
parent 25ba8ee489
commit cebcec5e63
1 changed files with 17 additions and 1 deletions
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18
ports/atmel-samd/common-hal/busio/I2C.c
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@ -34,6 +34,7 @@
#include "peripherals.h"
#include "pins.h"
#include "shared-bindings/microcontroller/__init__.h"
// Number of times to try to send packet if failed.
@ -77,10 +78,21 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
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_DOWN);
gpio_set_pin_pull_mode(scl->pin, GPIO_PULL_DOWN);
common_hal_mcu_delay_us(10);
gpio_set_pin_pull_mode(sda->pin, GPIO_PULL_OFF);
gpio_set_pin_pull_mode(scl->pin, GPIO_PULL_OFF);
// We must pull up within 3us to achieve 400khz.
common_hal_mcu_delay_us(3);
if (!gpio_get_pin_level(sda->pin) || !gpio_get_pin_level(scl->pin)) {
reset_pin(sda->pin);
reset_pin(scl->pin);
mp_raise_RuntimeError("SDA or SCL needs a pull up");
}
gpio_set_pin_function(sda->pin, sda_pinmux);
@ -90,13 +102,17 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
samd_peripherals_sercom_clock_init(sercom, sercom_index);
if (i2c_m_sync_init(&self->i2c_desc, sercom) != ERR_NONE) {
mp_raise_OSError(MP_EIO);
reset_pin(sda->pin);
reset_pin(scl->pin);
mp_raise_OSError(MP_EIO);
}
// clkrate is always 0. baud_rate is in kHz.
// Frequency must be set before the I2C device is enabled.
if (i2c_m_sync_set_baudrate(&self->i2c_desc, 0, frequency / 1000) != ERR_NONE) {
reset_pin(sda->pin);
reset_pin(scl->pin);
mp_raise_ValueError("Unsupported baudrate");
}