From 0f3c0ffbb01ceb6554a06494ab6ffcbe6d736182 Mon Sep 17 00:00:00 2001
From: Robert Foss <dev@robertfoss.se>
Date: Wed, 9 Dec 2015 16:35:50 -0500
Subject: [PATCH] Added support for the APA102 LED.

---
 app/include/user_modules.h |   1 +
 app/modules/apa102.c       | 114 +++++++++++++++++++++++++++++++++++++
 docs/en/modules/apa102.md  |  31 ++++++++++
 3 files changed, 146 insertions(+)
 create mode 100644 app/modules/apa102.c
 create mode 100644 docs/en/modules/apa102.md

diff --git a/app/include/user_modules.h b/app/include/user_modules.h
index fecdad7c..27c4d4c1 100644
--- a/app/include/user_modules.h
+++ b/app/include/user_modules.h
@@ -14,6 +14,7 @@
 #ifndef LUA_CROSS_COMPILER
 
 #define LUA_USE_MODULES_ADC
+//#define LUA_USE_MODULES_APA102
 #define LUA_USE_MODULES_BIT
 //#define LUA_USE_MODULES_BMP085
 #define LUA_USE_MODULES_CJSON
diff --git a/app/modules/apa102.c b/app/modules/apa102.c
new file mode 100644
index 00000000..7f509f1e
--- /dev/null
+++ b/app/modules/apa102.c
@@ -0,0 +1,114 @@
+#include "lualib.h"
+#include "lauxlib.h"
+#include "platform.h"
+#include "lrotable.h"
+#include "c_stdlib.h"
+#include "c_string.h"
+#include "user_interface.h"
+
+
+#define NOP asm volatile(" nop \n\t")
+
+
+static inline void apa102_send_byte(uint32_t data_pin, uint32_t clock_pin, uint8_t byte) {
+  int i;
+  for (i = 0; i < 8; i++) {
+    if (byte & 0x80) {
+      GPIO_OUTPUT_SET(data_pin, PLATFORM_GPIO_HIGH); // Set pin high
+    } else {
+      GPIO_OUTPUT_SET(data_pin, PLATFORM_GPIO_LOW); // Set pin low
+    }
+    GPIO_OUTPUT_SET(clock_pin, PLATFORM_GPIO_HIGH); // Set pin high
+    byte <<= 1;
+    NOP;
+    NOP;
+    GPIO_OUTPUT_SET(clock_pin, PLATFORM_GPIO_LOW); // Set pin low
+    NOP;
+    NOP;
+  }
+}
+
+
+static void apa102_send_buffer(uint32_t data_pin, uint32_t clock_pin, uint32_t *buf, uint32_t nbr_frames) {
+  int i;
+
+  // Send 32-bit Start Frame that's all 0x00
+  apa102_send_byte(data_pin, clock_pin, 0x00);
+  apa102_send_byte(data_pin, clock_pin, 0x00);
+  apa102_send_byte(data_pin, clock_pin, 0x00);
+  apa102_send_byte(data_pin, clock_pin, 0x00);
+
+  // Send 32-bit LED Frames
+  for (i = 0; i < nbr_frames; i++) {
+    uint8_t *byte = (uint8_t *) buf++;
+
+    // Set the first 3 bits of that byte to 1.
+    // This makes the lua interface easier to use since you
+    // don't have to worry about creating invalid LED Frames.
+    byte[0] |= 0xE0;
+    apa102_send_byte(data_pin, clock_pin, byte[0]);
+    apa102_send_byte(data_pin, clock_pin, byte[1]);
+    apa102_send_byte(data_pin, clock_pin, byte[2]);
+    apa102_send_byte(data_pin, clock_pin, byte[3]);
+  }
+
+  // Send 32-bit End Frames
+  uint32_t required_postamble_frames = (nbr_frames + 1) / 2;
+  for (i = 0; i < required_postamble_frames; i++) {
+    apa102_send_byte(data_pin, clock_pin, 0xFF);
+    apa102_send_byte(data_pin, clock_pin, 0xFF);
+    apa102_send_byte(data_pin, clock_pin, 0xFF);
+    apa102_send_byte(data_pin, clock_pin, 0xFF);
+  }
+}
+
+
+// Lua: apa102.write(data_pin, clock_pin, "string")
+// Byte quads in the string are interpreted as (brightness, B, G, R) values.
+// Only the first 5 bits of the brightness value is actually used (0-31).
+// This function does not corrupt your buffer.
+//
+// apa102.write(1, 3, string.char(31, 0, 255, 0)) uses GPIO5 for DATA and GPIO0 for CLOCK and sets the first LED green, with the brightness 31 (out of 0-32)
+// apa102.write(5, 6, string.char(255, 0, 0, 255):rep(10)) uses GPIO14 for DATA and GPIO12 for CLOCK and sets ten LED to red, with the brightness 31 (out of 0-32).
+//                                                         Brightness values are clamped to 0-31.
+static int apa102_write(lua_State* L) {
+  uint8_t data_pin = luaL_checkinteger(L, 1);
+  MOD_CHECK_ID(gpio, data_pin);
+  uint32_t alt_data_pin = pin_num[data_pin];
+
+  uint8_t clock_pin = luaL_checkinteger(L, 2);
+  MOD_CHECK_ID(gpio, clock_pin);
+  uint32_t alt_clock_pin = pin_num[clock_pin];
+
+  size_t buf_len;
+  const char *buf = luaL_checklstring(L, 3, &buf_len);
+  uint32_t nbr_frames = buf_len / 4;
+
+  if (nbr_frames > 100000) {
+    return luaL_error(L, "The supplied buffer is too long, and might cause the callback watchdog to bark.");
+  }
+
+  // Initialize the output pins
+  platform_gpio_mode(data_pin, PLATFORM_GPIO_OUTPUT, PLATFORM_GPIO_FLOAT);
+  GPIO_OUTPUT_SET(alt_data_pin, PLATFORM_GPIO_HIGH); // Set pin high
+  platform_gpio_mode(clock_pin, PLATFORM_GPIO_OUTPUT, PLATFORM_GPIO_FLOAT);
+  GPIO_OUTPUT_SET(alt_clock_pin, PLATFORM_GPIO_LOW); // Set pin low
+
+  // Send the buffers
+  apa102_send_buffer(alt_data_pin, alt_clock_pin, (uint32_t *) buf, (uint32_t) nbr_frames);
+  return 0;
+}
+
+
+#define MIN_OPT_LEVEL 2
+#include "lrodefs.h"
+const LUA_REG_TYPE apa102_map[] =
+{
+  { LSTRKEY( "write" ), LFUNCVAL( apa102_write )},
+  { LNILKEY, LNILVAL}
+};
+
+LUALIB_API int luaopen_apa102(lua_State *L) {
+  LREGISTER(L, "apa102", apa102_map);
+  return 1;
+}
diff --git a/docs/en/modules/apa102.md b/docs/en/modules/apa102.md
new file mode 100644
index 00000000..00ccbd9e
--- /dev/null
+++ b/docs/en/modules/apa102.md
@@ -0,0 +1,31 @@
+# APA102 Module
+
+## apa102.write()
+Send ABGR data in 8 bits to a APA102 chain.
+
+#### Syntax
+`apa102.write(data_pin, clock_pin, string)`
+
+#### Parameters
+- `data_pin` any GPIO pin 0, 1, 2, ...
+- `clock_pin` any GPIO pin 0, 1, 2, ...
+- `string` payload to be sent to one or more APA102 LEDs.
+  It should be composed from a AGRB quadruplet per element.
+    - `A1` the first pixel's Intensity channel (0-31)
+    - `B1` the first pixel's Blue channel (0-255)<br />
+    - `G1` the first pixel's Green channel (0-255)
+    - `R1` the first pixel's Red channel (0-255)
+    ... You can connect a lot of APA102 ...
+    - `A1`, `G2`, `R2`, `B2` are the next APA102s Intensity, Blue, Green and channel parameters
+
+#### Returns
+`nil`
+
+```lua
+a = 31
+g = 0
+r = 255
+b = 0
+leds_bgr = string.char(a, g, r, b, a, g, r, b) 
+apa102.write(2, 3, leds_abgr) -- turn two APA102s to red, connected to data_pin 2 and clock_pin 3
+```