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Merge pull request #719 from tannewt/fix_i2c_hang

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Fix I2C init hang when the SCL pin is pulled low.
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Kattni 2018-03-26 20:08:14 -04:00 committed by GitHub
commit 77938db8c8
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1 changed files with 30 additions and 7 deletions
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35
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.
@ -72,24 +73,46 @@ 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_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);
gpio_set_pin_function(scl->pin, scl_pinmux);
// Set up I2C clocks on sercom.
samd_peripherals_sercom_clock_init(sercom, sercom_index);
if (i2c_m_sync_init(&self->i2c_desc, sercom) != ERR_NONE) {
reset_pin(sda->pin);
reset_pin(scl->pin);
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.
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");
}