Fix LP_I2C_NUM_0 support: use LP_I2C_SCLK_DEFAULT clock source#13
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i2c_setup_port always passed I2C_CLK_SRC_DEFAULT to i2c_new_master_bus, which returns ESP_ERR_NOT_SUPPORTED for LP_I2C_NUM_0. LP I2C requires LP_I2C_SCLK_DEFAULT instead. clk_source and lp_source_clk are union members in i2c_master_bus_config_t sharing the same memory, but LP_I2C_SCLK_DEFAULT is not a valid i2c_clock_source_t value so the driver rejects the HP default when given an LP port number. Fix: set clk_source = LP_I2C_SCLK_DEFAULT when dev->port == LP_I2C_NUM_0, guarded by SOC_LP_I2C_SUPPORTED so it compiles cleanly on chips without an LP I2C peripheral. All HP bus behaviour is unchanged. Fixes: esp-idf-lib#12
This was referenced May 27, 2026
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Summary
Fixes #12.
i2c_setup_porthardcoded.clk_source = I2C_CLK_SRC_DEFAULTin thei2c_master_bus_config_tinitializer. ForLP_I2C_NUM_0this is the wrongvalue:
clk_sourceandlp_source_clkare union members in the struct, andLP_I2C_SCLK_DEFAULTis not a validi2c_clock_source_t— passingI2C_CLK_SRC_DEFAULTfor an LP port causesi2c_new_master_busto returnESP_ERR_NOT_SUPPORTED.The fix detects the LP port and sets
LP_I2C_SCLK_DEFAULT, guarded by#if SOC_LP_I2C_SUPPORTEDso it is a no-op on chips without LP_I2C.Testing
Validated on ESP32-C6 (the only current ESP-IDF target with
SOC_LP_I2C_SUPPORTED):a firmware project using i2cdev devices (
INA219,BQ27220) onLP_I2C_NUM_0(GPIO6/GPIO7) now initialises correctly. Previously the first i2cdev transaction
on the LP port returned
ESP_ERR_NOT_SUPPORTED.HP I2C behaviour on ESP32-C6 and ESP32-S3 is unchanged — the
elsebranchkeeps
I2C_CLK_SRC_DEFAULTfor all HP ports, and the#if SOC_LP_I2C_SUPPORTEDguard means the new code is not compiled on chips without LP_I2C.
Notes
.clk_source = LP_I2C_SCLK_DEFAULT(not the
.lp_source_clkfield name) — both field names work because they areunion members, but the value is what matters.
for context on why we ended up pinning the fork as a submodule while waiting for
this PR to land.