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[pca9554] Reduce I2C bus usage with lazy input caching

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This commit is contained in:
J. Nick Koston
2025-09-04 10:33:05 -05:00
parent c7ee727af4
commit faca78aeb9
2 changed files with 9 additions and 16 deletions
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21
esphome/components/pca9554/pca9554.cpp
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@@ -37,10 +37,9 @@ void PCA9554Component::setup() {
} }
void PCA9554Component::loop() { void PCA9554Component::loop() {
// The read_inputs_() method will cache the input values from the chip. // Invalidate the cache at the start of each loop.
this->read_inputs_(); // The actual read will happen on demand in digital_read()
// Clear all the previously read flags. this->cache_valid_ = false;
this->was_previously_read_ = 0x00;
} }
void PCA9554Component::dump_config() { void PCA9554Component::dump_config() {
@@ -55,16 +54,10 @@ void PCA9554Component::dump_config() {
} }
bool PCA9554Component::digital_read(uint8_t pin) { bool PCA9554Component::digital_read(uint8_t pin) {
// Note: We want to try and avoid doing any I2C bus read transactions here // Read the inputs once per loop on demand and cache the result
// to conserve I2C bus bandwidth. So what we do is check to see if we if (!this->cache_valid_ && this->read_inputs_()) {
// have seen a read during the time esphome is running this loop. If we have, this->cache_valid_ = true;
// we do an I2C bus transaction to get the latest value. If we haven't }
// we return a cached value which was read at the time loop() was called.
if (this->was_previously_read_ & (1 << pin))
this->read_inputs_(); // Force a read of a new value
// Indicate we saw a read request for this pin in case a
// read happens later in the same loop.
this->was_previously_read_ |= (1 << pin);
return this->input_mask_ & (1 << pin); return this->input_mask_ & (1 << pin);
} }

4
esphome/components/pca9554/pca9554.h
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@@ -45,8 +45,8 @@ class PCA9554Component : public Component, public i2c::I2CDevice {
uint16_t output_mask_{0x00}; uint16_t output_mask_{0x00};
/// The state of the actual input pin states - 1 means HIGH, 0 means LOW /// The state of the actual input pin states - 1 means HIGH, 0 means LOW
uint16_t input_mask_{0x00}; uint16_t input_mask_{0x00};
/// Flags to check if read previously during this loop /// Cache validity flag - true if we've read inputs this loop cycle
uint16_t was_previously_read_ = {0x00}; bool cache_valid_{false};
/// Storage for last I2C error seen /// Storage for last I2C error seen
esphome::i2c::ErrorCode last_error_; esphome::i2c::ErrorCode last_error_;
}; };