Presto display driver

.gitignore

@@ -58,3 +58,8 @@ dkms.conf
 build*/
 doc/
 Testing/
+
+# Miscellaneous
+*.log
+*.tmp
+.DS_Store

doxygen/modules_diagram.dox.inc

@@ -13,7 +13,7 @@ digraph modules {
   Cond       [label="Condition Variables",  URL="\ref SystemSyncCond"];
   WaitGroup  [label="Wait Groups",          URL="\ref SystemSyncWaitgroup"];
   Atomic     [label="Atomic Operations",    URL="\ref SystemAtomic"];
-  Data        [label="Data", URL="\ref SystemData"];
+  Data        [label="Data",                     URL="\ref SystemData"];
   DataRune    [label="Runes",                    URL="\ref SystemDataRune"];
   DataString  [label="Strings",                  URL="\ref SystemDataString"];
   DataScanner [label="Scanner",                  URL="\ref SystemDataScanner"];
@@ -53,8 +53,9 @@ digraph modules {
   FT6236      [label="FT6236",                   URL="\ref FT6236"];
   STMPE610    [label="STMPE610",                 URL="\ref STMPE610"];
   ILI9341     [label="ILI9341",                  URL="\ref ILI9341"];
+  ST7701      [label="ST7701",                   URL="\ref ST7701"];
   SDL         [label="SDL",                      URL="\ref SDL"];
-  Pixels      [label="Pixels",                    URL="\ref Pixel"];
+  Pixels      [label="Pixels",                   URL="\ref Pixel"];
   PixelDisplay [label="Display",                 URL="\ref PixelDisplay"];
   PixelBitmap [label="Bitmap",                   URL="\ref PixelBitmap"];
   Application [label="Application",              URL="\ref Application"];
@@ -111,6 +112,7 @@ digraph modules {
   Sensor -> BME680;
   Display -> ILI9341;
   Display -> SDL;
+  Display -> ST7701;
   Pixels -> PixelDisplay;
   Pixels -> PixelBitmap;
   Application -> HID;

include/picofuse/dev.h

@@ -35,4 +35,5 @@
 #include "dev/ft6236.h"
 #include "dev/ili9341.h"
 #include "dev/sdl.h"
+#include "dev/st7701.h"
 #include "dev/stmpe610.h"

include/picofuse/dev/st7701.h

@@ -0,0 +1,74 @@
+/**
+ * @file st7701.h
+ * @brief ST7701 TFT LCD controller interface.
+ * @defgroup ST7701 ST7701
+ * @ingroup Display
+ */
+#pragma once
+
+#include <picofuse/hw.h>
+#include <picofuse/pix.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+///////////////////////////////////////////////////////////////////////////////
+// TYPES
+
+/**
+ * @brief Optional ST7701 initialization options.
+ * @ingroup ST7701
+ */
+typedef struct {
+  uint16_t rotation;
+} dev_st7701_config_t;
+
+///////////////////////////////////////////////////////////////////////////////
+// LIFECYCLE
+
+/** @name Lifecycle
+ * @{ */
+
+/**
+ * @brief Fill an ST7701 config struct with safe defaults.
+ * @ingroup ST7701
+ * @param config Config structure to initialize.
+ */
+void dev_st7701_default_config(dev_st7701_config_t *config);
+
+/**
+ * @brief Initialize an ST7701-driven display over SPI.
+ * @ingroup ST7701
+ * @param device SPI device handle. This panel has no D/CX GPIO - `device`
+ * must be a hw_spi_init() handle configured with `bits_per_word = 9`,
+ * command/data select packed as the 9th bit of every word (see
+ * hw_deviceio_xfr()).
+ * @param size Panel resolution.
+ * @param bl_pin Optional GPIO handle for the backlight. Pass `NULL` if
+ * the backlight isn't software-controlled.
+ * @param config Optional pointer to initialization options. Pass `NULL`
+ * to use default values.
+ * @return display handle, or `NULL` on failure
+ */
+pix_display_t *dev_st7701_init(hw_deviceio_t *device, pix_size_t size,
+                               hw_gpio_t *bl_pin,
+                               const dev_st7701_config_t *config);
+
+/** @} */
+
+///////////////////////////////////////////////////////////////////////////////
+// METHODS
+
+/** @name Methods
+ * @{ */
+
+/**
+ * @brief Set the backlight brightness.
+ * @ingroup ST7701
+ * @param display Display handle from dev_st7701_init().
+ * @param brightness Brightness from `0` (off) to `255` (full).
+ * @return `false` if `display` wasn't created by dev_st7701_init(), or has
+ * no backlight pin.
+ */
+bool dev_st7701_set_backlight(pix_display_t *display, uint8_t brightness);
+
+/** @} */

include/picofuse/hw/deviceio.h

@@ -103,18 +103,30 @@ hw_deviceio_bus_t hw_deviceio_bus(const hw_deviceio_t *device);
  * @brief Perform a raw, bidirectional transfer.
  * @ingroup DeviceIO
  * @param device Device handle.
- * @param data Buffer used for transmitted and received bytes.
- * @param tx Number of bytes to transmit from `data`.
- * @param rx Number of bytes to receive into `data + tx`.
+ * @param data Buffer used for transmitted and received words - `uint8_t*`
+ * unless noted otherwise below.
+ * @param tx Number of words to transmit from `data`.
+ * @param rx Number of words to receive into `data + tx * word_size`.
  * @param timeout_ms Timeout in milliseconds for the operation. Set to `0`
  * to use the backend's default transfer path.
- * @return Number of bytes transferred, or `0` on failure.
+ * @return Number of words transferred, or `0` on failure.
  *
  * Supports write-only (`tx > 0, rx == 0`), read-only (`tx == 0, rx > 0`),
  * and write-then-read (`tx > 0, rx > 0`) transfers. The exact semantics of
  * a write-then-read - a repeated start on I2C, a continuous chip-select
  * assertion on SPI - are defined by whichever bus `device` is actually
  * bound to.
+ *
+ * A "word" here is 1 byte for every I2C device (no framing concept
+ * applies) and for an SPI device left at its default `hw_spi_config_t::
+ * bits_per_word` (8) - `data` is `uint8_t*`, and `tx`/`rx` count bytes
+ * exactly as before. For an SPI device configured with `bits_per_word`
+ * above 8 (9-16, e.g. a display panel that packs a command/data select
+ * bit as the 9th bit of every word), a word is 2 bytes instead - `data`
+ * must then be `uint16_t*`, and `tx`/`rx` count 16-bit words, not bytes
+ * (so the underlying buffer needs `(tx + rx) * 2` bytes of storage, not
+ * `tx + rx`). Check whichever `hw_*_init()` built `device` for what its
+ * own word size is.
  */
 size_t hw_deviceio_xfr(hw_deviceio_t *device, void *data, size_t tx, size_t rx,
                        uint32_t timeout_ms);

include/picofuse/hw/spi.h

@@ -56,7 +56,9 @@ typedef enum {
 typedef struct {
   bool cs_active_low;    ///< True when chip-select is active low.
   hw_spi_mode_t mode;    ///< SPI mode selection.
-  uint8_t bits_per_word; ///< SPI frame size in bits.
+  uint8_t bits_per_word; ///< SPI frame size in bits (4-16). Above 8 changes
+                        ///< hw_deviceio_xfr()'s own word size for this
+                        ///< device - see its doc.
 } hw_spi_config_t;
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -88,7 +90,8 @@ hw_deviceio_t *hw_spi_init_default(uint32_t baud_rate,
  * @param index SPI adapter index to use.
  * @param sck_pin GPIO handle for SCK.
  * @param tx_pin GPIO handle for MOSI.
- * @param rx_pin GPIO handle for MISO.
+ * @param rx_pin Optional GPIO handle for MISO. Pass `NULL` for a
+ * write-only device with no MISO line (e.g. a 3-wire display panel).
  * @param cs_pin Optional GPIO handle for CS. Pass NULL to leave CS unmanaged.
  * @param baud_rate Desired SPI clock rate in Hz.
  * @param config Optional pointer to extended SPI configuration. Pass `NULL`

src/picofuse/dev/CMakeLists.txt

@@ -1,8 +1,14 @@
 
-# SDL support
-find_package(PkgConfig QUIET)
-if(PkgConfig_FOUND)
-    pkg_check_modules(SDL2 QUIET IMPORTED_TARGET sdl2)
+# SDL support - host-only. pkg-config always searches the host's own
+# library paths regardless of cross-compilation, so on a Pico build this
+# would otherwise "find" and try to link against the host's native SDL2
+# (wrong ABI/arch entirely) - and SDL2 makes no sense on Pico anyway, with
+# no windowing system to speak of.
+if(NOT DEFINED PICO_BOARD)
+    find_package(PkgConfig QUIET)
+    if(PkgConfig_FOUND)
+        pkg_check_modules(SDL2 QUIET IMPORTED_TARGET sdl2)
+    endif()
 endif()
 if(SDL2_FOUND)
     message(STATUS "Found SDL2: enabling SDL display backend")
@@ -22,6 +28,7 @@ picofuse_library(
         stmpe610/stmpe610.c
         stmpe610/hid.c
         ${_sdl_src}
+        st7701/st7701.c
 )
 
 target_include_directories(picofuse-dev PRIVATE ${CMAKE_SOURCE_DIR}/include)