Add a basic i2c gpio expander implementation

main/CMakeLists.txt

@@ -1,2 +1,2 @@
-idf_component_register(SRCS "gay-ipod-fw.cpp"
+idf_component_register(SRCS "gay-ipod-fw.cpp" "gpio-expander.cpp"
                     INCLUDE_DIRS ".")

main/gay-ipod-fw.cpp

@@ -1,10 +1,12 @@
 #include <stdio.h>
 
+#include "gpio-expander.h"
 #include "esp_log.h"
 #include "driver/gpio.h"
 #include "driver/i2c.h"
 #include "driver/spi_common.h"
 #include "driver/spi_master.h"
+#include "gpio-expander.h"
 #include "hal/gpio_types.h"
 #include "hal/spi_types.h"
 
@@ -83,4 +85,9 @@ extern "C" void app_main(void)
   ESP_LOGI(TAG, "Initialising peripherals");
   init_i2c();
   init_spi();
+
+  gay_ipod::GpioExpander expander;
+  expander.Write();
+
+  while (1) {}
 }

main/gpio-expander.cpp

@@ -0,0 +1,67 @@
+#include "gpio-expander.h"
+
+namespace gay_ipod {
+
+GpioExpander::GpioExpander() {
+}
+
+GpioExpander::~GpioExpander() {
+}
+
+esp_err_t GpioExpander::Write() {
+  i2c_cmd_handle_t handle = i2c_cmd_link_create();
+  if (handle == NULL) {
+    return ESP_ERR_NO_MEM;
+  }
+
+  // Technically enqueuing these commands could fail, but we don't worry about
+  // it because that would indicate some really very badly wrong more generally.
+  i2c_master_start(handle);
+  i2c_master_write_byte(handle, (PCA8575_ADDRESS << 1 | I2C_MASTER_WRITE), true);
+  i2c_master_write_byte(handle, port_a_, true);
+  i2c_master_write_byte(handle, port_b_, true);
+  i2c_master_stop(handle);
+
+  // TODO: timeout
+  esp_err_t ret = i2c_master_cmd_begin(0, handle, 0);
+
+  i2c_cmd_link_delete(handle);
+  return ret;
+}
+
+esp_err_t GpioExpander::Read() {
+  i2c_cmd_handle_t handle = i2c_cmd_link_create();
+  if (handle == NULL) {
+    return ESP_ERR_NO_MEM;
+  }
+
+  // Technically enqueuing these commands could fail, but we don't worry about
+  // it because that would indicate some really very badly wrong more generally.
+  i2c_master_start(handle);
+  i2c_master_write_byte(handle, (PCA8575_ADDRESS << 1 | I2C_MASTER_READ), true);
+  i2c_master_read_byte(handle, &input_a_, I2C_MASTER_ACK);
+  i2c_master_read_byte(handle, &input_b_, I2C_MASTER_LAST_NACK);
+  i2c_master_stop(handle);
+
+  // TODO: timeout
+  esp_err_t ret = i2c_master_cmd_begin(0, handle, 0);
+
+  i2c_cmd_link_delete(handle);
+  return ret;
+}
+
+bool GpioExpander::charge_power_ok(void) {
+  // Active-low.
+  return (input_a_ & (1 << 4)) == 0;
+}
+
+bool GpioExpander::headphone_detect(void) {
+  // Active-low.
+  return (input_b_ & (1 << 0)) == 0; // TODO.
+}
+
+uint8_t GpioExpander::key_states(void) {
+  return input_b_ & 0b00111111;
+}
+
+} // namespace gay_ipod

main/gpio-expander.h

@@ -0,0 +1,46 @@
+#ifndef GPIO_EXPANDER_H
+#define GPIO_EXPANDER_H
+
+#include <stdint.h>
+
+#include "esp_check.h"
+#include "esp_err.h"
+#include "driver/i2c.h"
+
+#define PCA8575_ADDRESS (0x20)
+
+namespace gay_ipod {
+
+/**
+ * PCA8575
+ */
+class GpioExpander {
+  public:
+    GpioExpander();
+    ~GpioExpander();
+
+    esp_err_t Write(void);
+    esp_err_t Read(void);
+
+    bool charge_power_ok(void);
+    bool headphone_detect(void);
+    uint8_t key_states(void);
+
+    // Not copyable or movable.
+    // TODO: maybe this could be movable?
+    GpioExpander(const GpioExpander&) = delete;
+    GpioExpander& operator=(const GpioExpander&) = delete;
+
+  private:
+    // All power switches low, both CS pins high, active-low PWR_OK high.
+    uint8_t port_a_ = 0b00001011;
+    // DAC mute output low, everything eelse is input and so held high.
+    uint8_t port_b_ = 0b10111111;
+
+    uint8_t input_a_ = 0;
+    uint8_t input_b_ = 0;
+};
+
+} // namespace gay_ipod
+
+#endif