Merge pull request #164 from ourairquality/i2c-open-drain
i2c: use open drain outputs.
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commit
38375e218a
1 changed files with 17 additions and 5 deletions
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@ -44,6 +44,19 @@ void i2c_init(uint8_t scl_pin, uint8_t sda_pin)
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started = false;
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g_scl_pin = scl_pin;
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g_sda_pin = sda_pin;
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// Just to prevent these pins floating too much if not connected.
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gpio_set_pullup(g_scl_pin, 1, 1);
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gpio_set_pullup(g_sda_pin, 1, 1);
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// I2C bus idle state.
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gpio_enable(g_scl_pin, GPIO_INPUT);
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gpio_enable(g_scl_pin, GPIO_INPUT);
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// Set the pins to a low output state for when they are configured
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// as outputs.
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gpio_write(g_scl_pin, 0);
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gpio_write(g_sda_pin, 0);
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}
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static void i2c_delay(void)
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@ -51,7 +64,8 @@ static void i2c_delay(void)
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sdk_os_delay_us(CLK_HALF_PERIOD_US);
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}
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// Set SCL as input and return current level of line, 0 or 1
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// Set SCL as input, allowing it to float high, and return current
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// level of line, 0 or 1
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static bool read_scl(void)
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{
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gpio_enable(g_scl_pin, GPIO_INPUT);
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@ -70,15 +84,13 @@ static bool read_sda(void)
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// Actively drive SCL signal low
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static void clear_scl(void)
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{
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gpio_enable(g_scl_pin, GPIO_OUTPUT);
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gpio_write(g_scl_pin, 0);
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gpio_enable(g_scl_pin, GPIO_OUT_OPEN_DRAIN);
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}
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// Actively drive SDA signal low
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static void clear_sda(void)
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{
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gpio_enable(g_sda_pin, GPIO_OUTPUT);
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gpio_write(g_sda_pin, 0);
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gpio_enable(g_sda_pin, GPIO_OUT_OPEN_DRAIN);
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}
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// Output start condition
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