1 files changed, 84 insertions, 0 deletions
diff --git a/src/drivers/include/i2c.hpp b/src/drivers/include/i2c.hpp
new file mode 100644
index 00000000..db554f5d
--- /dev/null
+++ b/src/drivers/include/i2c.hpp
@@ -0,0 +1,84 @@
+#pragma once
+
+#include <cstdint>
+
+#include "driver/i2c.h"
+#include "hal/i2c_types.h"
+
+namespace gay_ipod {
+
+/*
+ * Convenience wrapper for performing an I2C transaction with a reasonable
+ * preconfigured timeout, automatic management of a heap-based command buffer,
+ * and a terser API for enqueuing bytes.
+ *
+ * Any error codes from the underlying ESP IDF are treated as fatal, since they
+ * typically represent invalid arguments or OOMs.
+ */
+class I2CTransaction {
+ public:
+  static const uint8_t kI2CTimeout = 100 / portTICK_RATE_MS;
+
+  I2CTransaction();
+  ~I2CTransaction();
+
+  /*
+   * Executes all enqueued commands, returning the result code. Possible error
+   * codes, per the ESP-IDF docs:
+   *
+   * ESP_OK Success
+   * ESP_ERR_INVALID_ARG Parameter error
+   * ESP_FAIL Sending command error, slave doesn’t ACK the transfer.
+   * ESP_ERR_INVALID_STATE I2C driver not installed or not in master mode.
+   * ESP_ERR_TIMEOUT Operation timeout because the bus is busy.
+   */
+  esp_err_t Execute();
+
+  /*
+   * Enqueues a start condition. May also be used for repeated start
+   * conditions.
+   */
+  I2CTransaction& start();
+  /* Enqueues a stop condition. */
+  I2CTransaction& stop();
+
+  /*
+   * Enqueues writing the given 7 bit address, followed by one bit indicating
+   * whether this is a read or write request.
+   *
+   * This command will expect an ACK before continuing.
+   */
+  I2CTransaction& write_addr(uint8_t addr, uint8_t op);
+
+  /*
+   * Enqueues one or more bytes to be written. The transaction will wait for
+   * an ACK to be returned before writing the next byte.
+   */
+  I2CTransaction& write_ack(uint8_t data);
+  template <typename... More>
+  I2CTransaction& write_ack(uint8_t data, More... more) {
+    write_ack(data);
+    write_ack(more...);
+    return *this;
+  }
+
+  /*
+   * Enqueues a read of one byte into the given uint8. Responds with the given
+   * ACK/NACK type.
+   */
+  I2CTransaction& read(uint8_t* dest, i2c_ack_type_t ack);
+
+  /* Returns the underlying command buffer. */
+  i2c_cmd_handle_t handle() { return handle_; }
+
+  // Cannot be moved or copied, since doing so is probably an error. Pass a
+  // reference instead.
+  I2CTransaction(const I2CTransaction&) = delete;
+  I2CTransaction& operator=(const I2CTransaction&) = delete;
+
+ private:
+  i2c_cmd_handle_t handle_;
+  uint8_t* buffer_;
+};
+
+}  // namespace gay_ipod