gpio expander pin change -> event!

2 files changed, 276 insertions, 0 deletions

diff --git a/src/drivers/gpios.cpp b/src/drivers/gpios.cpp
new file mode 100644
index 00000000..6689e2ea
--- /dev/null
+++ b/src/drivers/gpios.cpp
@@ -0,0 +1,148 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "gpios.hpp"
+
+#include <stdint.h>
+
+#include <cstdint>
+
+#include "driver/gpio.h"
+#include "hal/gpio_types.h"
+#include "i2c.hpp"
+
+namespace drivers {
+
+static const uint8_t kPca8575Address = 0x20;
+
+// Port A:
+// 0 - sd card mux switch
+// 1 - sd card mux enable (active low)
+// 2 - key up
+// 3 - key down
+// 4 - key lock
+// 5 - display reset (active low)
+// 6 - NC
+// 7 - sd card power (active low)
+// Default to SD card off, inputs high.
+static const uint8_t kPortADefault = 0b10111110;
+
+// Port B:
+// 0 - 3.5mm jack detect (active low)
+// 1 - headphone amp power enable
+// 2 - volume zero-cross detection
+// 3 - volume direction
+// 4 - volume left channel
+// 5 - volume right channel
+// 6 - NC
+// 7 - NC
+// Default input high, trs output low
+static const uint8_t kPortBDefault = 0b00000011;
+
+/*
+ * Convenience mehod for packing the port a and b bytes into a single 16 bit
+ * value.
+ */
+constexpr uint16_t pack(uint8_t a, uint8_t b) {
+  return ((uint16_t)b) << 8 | a;
+}
+
+/*
+ * Convenience mehod for unpacking the result of `pack` back into two single
+ * byte port datas.
+ */
+constexpr std::pair<uint8_t, uint8_t> unpack(uint16_t ba) {
+  return std::pair((uint8_t)ba, (uint8_t)(ba >> 8));
+}
+
+void interrupt_isr(void* arg) {
+  Gpios* instance = reinterpret_cast<Gpios*>(arg);
+  auto listener = instance->listener();
+  if (listener != nullptr) {
+    std::invoke(*listener);
+  }
+}
+
+auto Gpios::Create() -> Gpios* {
+  Gpios* instance = new Gpios();
+  // Read and write initial values on initialisation so that we do not have a
+  // strange partially-initialised state.
+  if (!instance->Flush() || !instance->Read()) {
+    return nullptr;
+  }
+  return instance;
+}
+
+Gpios::Gpios()
+    : ports_(pack(kPortADefault, kPortBDefault)),
+      inputs_(0),
+      listener_(nullptr) {
+  gpio_config_t config{
+      .pin_bit_mask = static_cast<uint64_t>(1) << GPIO_NUM_34,
+      .mode = GPIO_MODE_INPUT,
+      .pull_up_en = GPIO_PULLUP_ENABLE,
+      .pull_down_en = GPIO_PULLDOWN_DISABLE,
+      .intr_type = GPIO_INTR_NEGEDGE,
+  };
+  gpio_config(&config);
+  gpio_install_isr_service(ESP_INTR_FLAG_LOWMED | ESP_INTR_FLAG_SHARED |
+                           ESP_INTR_FLAG_IRAM);
+  gpio_isr_handler_add(GPIO_NUM_34, &interrupt_isr, this);
+}
+
+Gpios::~Gpios() {
+  gpio_isr_handler_remove(GPIO_NUM_34);
+  gpio_uninstall_isr_service();
+}
+
+auto Gpios::WriteBuffered(Pin pin, bool value) -> void {
+  if (value) {
+    ports_ |= (1 << static_cast<int>(pin));
+  } else {
+    ports_ &= ~(1 << static_cast<int>(pin));
+  }
+}
+
+auto Gpios::WriteSync(Pin pin, bool value) -> bool {
+  WriteBuffered(pin, value);
+  return Flush();
+}
+
+auto Gpios::Flush() -> bool {
+  std::pair<uint8_t, uint8_t> ports_ab = unpack(ports_);
+
+  I2CTransaction transaction;
+  transaction.start()
+      .write_addr(kPca8575Address, I2C_MASTER_WRITE)
+      .write_ack(ports_ab.first, ports_ab.second)
+      .stop();
+
+  return transaction.Execute() == ESP_OK;
+}
+
+auto Gpios::Get(Pin pin) const -> bool {
+  return (inputs_ & (1 << static_cast<int>(pin))) > 0;
+}
+
+auto Gpios::Read() -> bool {
+  uint8_t input_a, input_b;
+
+  I2CTransaction transaction;
+  transaction.start()
+      .write_addr(kPca8575Address, I2C_MASTER_READ)
+      .read(&input_a, I2C_MASTER_ACK)
+      .read(&input_b, I2C_MASTER_LAST_NACK)
+      .stop();
+
+  esp_err_t ret = transaction.Execute();
+  if (ret != ESP_OK) {
+    return false;
+  }
+  inputs_ = pack(input_a, input_b);
+  return true;
+}
+
+}  // namespace drivers
diff --git a/src/drivers/include/gpios.hpp b/src/drivers/include/gpios.hpp
new file mode 100644
index 00000000..32bbacf4
--- /dev/null
+++ b/src/drivers/include/gpios.hpp
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+#include <atomic>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <optional>
+#include <tuple>
+#include <utility>
+
+#include "driver/i2c.h"
+#include "esp_check.h"
+#include "esp_err.h"
+#include "esp_log.h"
+#include "freertos/FreeRTOS.h"
+
+namespace drivers {
+
+/**
+ * Wrapper for interfacing with the PCA8575 GPIO expander. Includes basic
+ * low-level pin setting methods, as well as higher level convenience functions
+ * for reading, writing, and atomically interacting with the SPI chip select
+ * pins.
+ *
+ * Each method of this class can be called safely from any thread, and all
+ * updates are guaranteed to be atomic. Any access to chip select related pins
+ * should be done whilst holding `cs_lock` (preferably via the helper methods).
+ */
+class IGpios {
+ public:
+  virtual ~IGpios() {}
+
+  /* Maps each pin of the expander to its number in a `pack`ed uint16. */
+  enum class Pin {
+    // Port A
+    kSdMuxSwitch = 0,
+    kSdMuxDisable = 1,
+    kKeyUp = 2,
+    kKeyDown = 3,
+    kKeyLock = 4,
+    kDisplayEnable = 5,
+    // 6 is unused
+    kSdPowerDisable = 7,
+
+    // Port B
+    kPhoneDetect = 8,
+    kAmplifierEnable = 9,
+    kSdCardDetect = 10,
+    // 11 through 15 are unused
+  };
+
+  /* Nicer value names for use with kSdMuxSwitch. */
+  enum SdController {
+    SD_MUX_ESP = 0,
+    SD_MUX_SAMD = 1,
+  };
+
+  /*
+   * Sets a single specific pin to the given value. `true` corresponds to
+   * HIGH, and `false` corresponds to LOW.
+   *
+   * This function will block until the pin has changed level.
+   */
+  virtual auto WriteSync(Pin, bool) -> bool = 0;
+
+  /*
+   * Returns the most recently cached value of the given pin.
+   */
+  virtual auto Get(Pin) const -> bool = 0;
+};
+
+class Gpios : public IGpios {
+ public:
+  static auto Create() -> Gpios*;
+  ~Gpios();
+
+  /*
+   * Sets a single specific pin to the given value. `true` corresponds to
+   * HIGH, and `false` corresponds to LOW.
+   *
+   * Calls to this method will be buffered in memory until a call to `Write()`
+   * is made.
+   */
+  auto WriteSync(Pin, bool) -> bool override;
+
+  virtual auto WriteBuffered(Pin, bool) -> void;
+
+  /**
+   * Sets the ports on the GPIO expander to the values currently represented
+   * in `ports`.
+   */
+  auto Flush(void) -> bool;
+
+  auto Get(Pin) const -> bool override;
+
+  /**
+   * Reads from the GPIO expander, populating `inputs` with the most recent
+   * values.
+   */
+  auto Read(void) -> bool;
+
+  auto listener() -> std::function<void(void)>* { return listener_; }
+
+  auto set_listener(std::function<void(void)>* l) -> void { listener_ = l; }
+
+  // Not copyable or movable. There should usually only ever be once instance
+  // of this class, and that instance will likely have a static lifetime.
+  Gpios(const Gpios&) = delete;
+  Gpios& operator=(const Gpios&) = delete;
+
+ private:
+  Gpios();
+
+  std::atomic<uint16_t> ports_;
+  std::atomic<uint16_t> inputs_;
+
+  std::function<void(void)>* listener_;
+};
+
+}  // namespace drivers