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I2C: sample SDA earlier #3040

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I2C: sample SDA earlier #3040

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21 changes: 20 additions & 1 deletion esp-hal/src/i2c/master/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,7 @@ pub enum BusTimeout {
Disabled,

/// Timeout in bus clock cycles.
//#[strum(to_string = "{0} bus clock cycles")] // FIXME uncomment when https://github.com/Peternator7/strum/pull/407 is released
BusCycles(u32),
}

Expand Down Expand Up @@ -1140,6 +1141,24 @@ fn configure_clock(
scl_stop_hold_time: u32,
timeout: BusTimeout,
) -> Result<(), ConfigError> {
debug!(
"Configuring I2C clock: sclk_div: {}, scl_low_period: {}, scl_high_period: {}, \
scl_wait_high_period: {}, sda_hold_time: {}, sda_sample_time: {}, \
scl_rstart_setup_time: {}, scl_stop_setup_time: {}, scl_start_hold_time: {}, \
scl_stop_hold_time: {}, timeout: {}",
sclk_div,
scl_low_period,
scl_high_period,
scl_wait_high_period,
sda_hold_time,
sda_sample_time,
scl_rstart_setup_time,
scl_stop_setup_time,
scl_start_hold_time,
scl_stop_hold_time,
timeout
);

unsafe {
// divider
#[cfg(any(esp32c2, esp32c3, esp32c6, esp32h2, esp32s3))]
Expand Down Expand Up @@ -1578,7 +1597,7 @@ impl Driver<'_> {
};
let scl_high = half_cycle - scl_wait_high;
let sda_hold = half_cycle / 4;
let sda_sample = half_cycle / 2 + scl_wait_high;
let sda_sample = half_cycle / 2;
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@bugadani bugadani Jan 27, 2025 •
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To be fair, I should probably remove the half_cycle/2 term instead. Technically, we can sample at any point after the rising edge, and scl_wait_high is supposed to be somewhat dependent on the hardware (i.e. it should be tunable, maybe). scl_wait_high represents the rising edge of the clock signal, after which the clock signal is high for scl_high. We should probably aim at the start/middle of the interval covered by scl_high.

Still, this should be good enough to test.

let setup = half_cycle;
let hold = half_cycle;

Expand Down
2 changes: 1 addition & 1 deletion qa-test/.cargo/config.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ rustflags = [
]

[env]
ESP_LOG = "info"
ESP_LOG = "debug"
ESP_HAL_EMBASSY_CONFIG_TIMER_QUEUE="multiple-integrated"

[unstable]
Expand Down
1 change: 1 addition & 0 deletions qa-test/src/bin/i2c_bmp180_calibration_data.rs
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Expand Up @@ -21,6 +21,7 @@ use esp_println::println;

#[main]
fn main() -> ! {
esp_println::logger::init_logger_from_env();
let peripherals = esp_hal::init(esp_hal::Config::default());

// Create a new peripheral object with the described wiring and standard
Expand Down
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