Touched up documentation, added example

Adafruit_RA8875_Due.cpp

@@ -11,6 +11,10 @@ typedef volatile union _SADDR_Type {
   Word raw;
 } SADDR_Type;
 
+/**
+ * Redef of the LLI as an entry in a row.
+ * Uses SADDR_Type union for easier debugging of what's in the SADDR field
+ */
 typedef volatile struct _RowFrame {
   SADDR_Type SADDR;
   Word DADDR;
@@ -30,6 +34,12 @@ typedef volatile struct _Row {
   }
 } Row;
 
+/**
+ * Gets a chunk of LLIs and treats them like an entire row of pixels. Good for bulk operations
+ * @param manager The DMA Manager
+ * @param row Which row to get
+ * @return The collection of frames as a row pointer, if within range. Nullptr otherwise
+ */
 static Row *get_row(DMAManager *manager, size_t row) {
   if (row * FRAMES_PER_LINE >= LLI_MAX_FRAMES) {
     return nullptr;

DMAManager.h

@@ -11,18 +11,33 @@
  * */
 /********************************/
 #ifndef FRAMES_PER_LINE
+/**
+ * The number of frames required to draw one line to the screen.
+ */
 #define FRAMES_PER_LINE 16
 #endif
 #ifndef LINES_PER_DMA
+/**
+ * The number of lines to be created/filled before the transfer starts
+ */
 #define LINES_PER_DMA 8
 #endif
 #ifndef WORKING_DATA_PER_LINE
+/**
+ * The number of bytes required to draw a line on the screen
+ */
 #define WORKING_DATA_PER_LINE 19
 #endif
 
 #define LLI_MAX_FRAMES (FRAMES_PER_LINE * LINES_PER_DMA)
 #define WORKING_DATA_SIZE (WORKING_DATA_PER_LINE * LINES_PER_DMA)
+/**
+ * The number of bytes needed to set the lower/upper bytes for one coordinate
+ */
 #define COORD_BUF_SPACE 4
+/**
+ * How long to wait / buffer the CS pin low or high
+ */
 #define DMA_CS_HIGH_TRANSFERS 8
 
 // Forward Declaration for class
@@ -66,8 +81,14 @@ typedef union DMAFunctionData {
 } DMAFunctionData;
 
 typedef struct DMACallbackData {
+  /**
+   * Data for use in the complete_cb function
+   */
   void *dataPtr;
 
+  /**
+   * Function called when transfers are complete
+   */
   void (*complete_cb)(void *);
 } DMACallbackData;
 
@@ -98,12 +119,19 @@ typedef struct DMA_Data {
 
   void volatile (*on_complete)(SpiDriver *spiDriver);
 
-
+  /**
+   * Resets the working data idx to 0. Doesn't actually clear data, just allows for overwrite
+   * @param full_clear Resets last_idx if true
+   */
   inline void clear_working_data(bool full_clear = false) {
     last_storage_idx = full_clear ? 0 : storage_idx;
     storage_idx = 0;
   }
 
+  /**
+   * Completely resets the DMA_Data instance
+   * @param full_reset Clears the last_data fields
+   */
   inline void reset(bool full_reset = false) {
     clear_working_data(full_reset);
     memset_volatile(&functionData, '\0', sizeof(DMAFunctionData));
@@ -116,10 +144,21 @@ typedef struct DMA_Data {
     on_complete = nullptr;
   }
 
+  /**
+   * @param size The amount of bytes needed to add
+   * @return true if there is space to add, false otherwise
+   */
   inline bool can_add_working_data(size_t size) const {
     return ((storage_idx - 1) + size) < WORKING_DATA_SIZE;
   }
 
+  /**
+   * Store sensitive data needed for DMA in a buffer for use during the transfers.
+   * Provides a size check to make sure the data can be added.
+   * @param buf The data to store
+   * @param size The number of bytes being added.
+   * @return uint8_t ptr to the location of the added data in the permanent buffer for future access.
+   */
   inline volatile uint8_t *add_working_data(const uint8_t *buf, size_t size) {
     if (!can_add_working_data(size)) {
       return nullptr;
@@ -165,6 +204,12 @@ class DMAManager {
 
   volatile LLI *get_next_blank_entry();
 
+  /**
+   * Gets an entry from the chain
+   * @param idx The idx to get.
+   * @param force If the index is out of 'size' bounds, will return nullptr unless force is true. Will return the index from the array
+   * @return The entry, if within range (or if force specified). Nullptr otherwise.
+   */
   volatile LLI *get_entry(size_t idx, bool force = false);
 
   inline volatile LLI *get_last() {
@@ -179,16 +224,28 @@ class DMAManager {
    * until we're done with the entire chain. This way if an element needs to be removed, all the `next` pointers won't need to be
    * rewritten.
    * This must be called before passing the beginning entry to DMA
+   * @return Ptr to the head of the list
    */
   volatile LLI *finalize();
 
+  /**
+   * Resets the size counter, does not zero memory
+   */
   void clear_frames();
 
+  /**
+   * Resets frames & working data
+   * @param full Clears the 'last_data' fields, if true
+   */
   void reset(bool full = false);
 
   size_t get_size() const;
 
-  bool can_add_entries(uint32_t entries) const;
+  /**
+   * @param entries The number of entries to check if available
+   * @return True if space, false otherwise
+   */
+  bool can_add_entries(size_t entries) const;
 
   DMA_Data *get_cur_data() {
     return &transaction_data;
@@ -197,18 +254,55 @@ class DMAManager {
   /************************
    * General purpose methods for adding SPI Frames, PIO Frames, etc.
    ************************/
+
+  /**
+   * @param state The state of the pin (Returns SODR for true, CODR for false)
+   * @param pin The pin to get the register for
+   * @return The address for the register.
+   */
   WoReg *get_pio_reg(bool state, uint8_t pin);
 
+  /**
+   * Gets the register for the chipselect pin
+   * @param state The state for the pin
+   * @return The address for the register
+   */
   WoReg *get_cs_pio_reg(bool state) {
     return get_pio_reg(state, _csPin);
   }
 
+  /**
+   * Adds an entry to toggle a pin high or low
+   * @param state The new state of the pin
+   * @param pin The pin number
+   * @param pin_mask_ptr A pointer to somewhere with the mask for that pin. The g_APinDescriptor will not work for this purpose.
+   * @param num_transfers How many transfers to send.
+   * @return Whether or not the entry was added to the buffer
+   */
   bool add_entry_pin_toggle(bool state, uint8_t pin, const uint32_t *pin_mask_ptr, size_t num_transfers = 2);
 
+  /**
+   * Specifically adds an entry to toggle the CS pin
+   * @param state The new state for the pin
+   * @param num_transfers How many transfers to send. The RA chip requires that CS be high for ~5 CLK cycles before going low again.
+   * @return Whether or not the entry was added to the buffer.
+   */
   bool add_entry_cs_pin_toggle(bool state, size_t num_transfers = 2);
 
+  /**
+   * Adds a generic SPI transfer to the list
+   * @param buf The start of the data to transfer.
+   * @param qty The number of bytes in the buffer.
+   * @return Whether or not the entry was added to the list
+   */
   bool add_entry_spi_transfer(volatile uint8_t *buf, size_t qty);
 
+  /**
+   * Adds all the necessary entries to draw a batch of pixels in an area.
+   * @param buf The buffer of pixels to add
+   * @param qty The number of pixels drawn
+   * @return uint8_t ptr to the start of the working data containing the draw commands (RA8875_CMDWRITE, DATAWRITE, etc)
+   */
   volatile uint8_t *add_entry_spi_draw_pixels(volatile uint8_t *buf, size_t qty);
 
   /**

DMAManagerDue.cpp

@@ -101,7 +101,7 @@ size_t DMAManager::get_size() const {
   return size;
 }
 
-bool DMAManager::can_add_entries(uint32_t entries) const {
+bool DMAManager::can_add_entries(size_t entries) const {
   bool result = size + entries <= LLI_MAX_FRAMES;
   return result;
 }

DMA_LLI.h

@@ -1,6 +1,13 @@
 #ifndef ADAFRUIT_RA8875_DMA_LLI_H
 #define ADAFRUIT_RA8875_DMA_LLI_H
 
+/*******************************************
+ *
+ * Add whatever includes necessary to implement your DMA controller logic.
+ * Currently only supports Arduino Due
+ *
+ ********************************************/
+
 
 #if defined(ARDUINO_SAM_DUE)
 

DMA_LLI_Due.h

@@ -5,6 +5,9 @@
 
 typedef uint32_t Word;
 
+/**
+ * Bitfield for CTRLA register.
+ */
 typedef volatile union _CTRLA_Field {
   _CTRLA_Field() : raw(0) {};
 
@@ -25,6 +28,9 @@ typedef volatile union _CTRLA_Field {
   Word raw;
 } CTRLA_Field;
 
+/**
+ * Bitfield for CTRLB Register
+ */
 typedef volatile union _CTRLB_Field {
   _CTRLB_Field() : _CTRLB_Field(0) {};
 

SpiDriver.h

@@ -36,26 +36,69 @@ class SpiDriver {
 public:
   explicit SpiDriver(uint8_t csPin, bool interrupts = false);
 
+  /**
+   * Activates the driver. Similar to SPI.beginTransaction or setting clock div, etc.
+   */
   void activate();
 
+  /**
+   * Deactivates the driver after activate(). Similar to SPI.endTransaction
+   */
   void deactivate();
 
+  /**
+   * Starts SPI. Usually wraps SPI.begin()
+   */
   void begin();
 
+  /**
+   * Ends SPI. Usually wraps SPI.end()
+   */
   void end();
 
+  /**
+   * Reads 1 byte from SPI
+   * @return Read data
+   */
   uint8_t receive();
 
+  /**
+   * Reads 2 bytes
+   * @return Bytes read
+   */
   uint16_t receive16();
 
+  /**
+   * Read n bytes
+   * @param buf buffer to read into
+   * @param count number of bytes to read
+   * @return A status code
+   */
   uint8_t receive(uint8_t *buf, size_t count);
 
+  /**
+   * Sends 1 byte
+   * @param data Data to send
+   */
   void send(uint8_t data);
 
+  /**
+   * Sends 2 bytes of data
+   * @param data The data to send
+   */
   void send16(uint16_t data);
 
+  /**
+   * Send n bytes
+   * @param buf The start of the buffer to send
+   * @param count Number of bytes
+   */
   void send(uint8_t *buf, size_t count);
 
+  /**
+   * Sets the clock speed for the SPI controller
+   * @param speed Speed in Hz
+   */
   inline void setClockSpeed(uint32_t speed) {
 #if SPI_HAS_TRANSACTION
     _spiSettings = SPISettings(speed, MSBFIRST, SPI_MODE0);
@@ -64,12 +107,23 @@ class SpiDriver {
 
 #if USE_DMA_INTERRUPT
 
+  /**
+   * Get the underlying DMA manager, if available.
+   * @return The Manager
+   */
   DMAManager *getDMAManager() {
     return &dmaManager;
   }
 
+  /**
+   * Sends a chain of DMA frames, if available
+   * @param head The start of the chain.
+   */
   void sendChain(volatile LLI *head);
 
+  /**
+   * Starts the next chain of DMA operations
+   */
   void nextDMA();
 
 #endif