Merge pull request #713 from christakahashi/hx711-support

Added support for the hx711 load cell ADC.

README.md

@@ -573,3 +573,13 @@ value = { true, { foo = "bar" } }
 json_text = cjson.encode(value)
 -- Returns: '[true,{"foo":"bar"}]'
 ```
+
+####Read an HX711 load cell ADC.
+Note: currently only chanel A with gain 128 is supported.
+The HX711 is an inexpensive 24bit ADC with programmable 128x, 64x, and 32x gain.  
+```lua
+	-- Initialize the hx711 with clk on pin 5 and data on pin 6
+	hx711.init(5,6)
+	-- Read ch A with 128 gain.
+	raw_data = hx711.read(0)
+```

app/include/user_modules.h

@@ -43,6 +43,7 @@
 #define LUA_USE_MODULES_SNTP
 //#define LUA_USE_MODULES_BMP085
 #define LUA_USE_MODULES_TSL2561
+//#define LUA_USE_MODULES_HX711
 
 #endif /* LUA_USE_MODULES */
 

app/modules/hx711.c

@@ -0,0 +1,81 @@
+#include "lualib.h"
+#include "lauxlib.h"
+#include "platform.h"
+#include "auxmods.h"
+#include "lrotable.h"
+#include "c_stdlib.h"
+#include "c_string.h"
+#include "user_interface.h"
+static uint8_t data_pin;
+static uint8_t clk_pin;
+
+/*Lua: hx711.init(clk_pin,data_pin)*/
+static int hx711_init(lua_State* L) {
+  clk_pin = luaL_checkinteger(L,1);
+  data_pin = luaL_checkinteger(L,2);
+  MOD_CHECK_ID( gpio, clk_pin );
+  MOD_CHECK_ID( gpio, data_pin );
+
+  platform_gpio_mode(clk_pin, PLATFORM_GPIO_OUTPUT, PLATFORM_GPIO_FLOAT);
+  platform_gpio_mode(data_pin, PLATFORM_GPIO_INPUT, PLATFORM_GPIO_FLOAT);
+  platform_gpio_write(clk_pin,1);//put chip to sleep.
+  return 0;
+}
+
+#define HX711_MAX_WAIT 1000000
+/*will only read chA@128gain*/
+/*Lua: result = hx711.read()*/
+static int ICACHE_FLASH_ATTR hx711_read(lua_State* L) {
+  uint32_t i;
+  int32_t data = 0;
+  //TODO: double check init has happened first.
+
+  //wakeup hx711
+  platform_gpio_write(clk_pin,0);
+  
+  //wait for data ready.  or time out.
+  //TODO: set pin inturrupt and come back to it.  This may take up to 1/10 sec
+  //        or maybe just make an async version too and have both available.
+	WRITE_PERI_REG(0x60000914, 0x73); //clear WDT... this may take a while.
+  for (i = 0; i<HX711_MAX_WAIT && platform_gpio_read(data_pin)==1;i++){
+    asm ("nop");
+  }
+  
+  //Handle timeout error
+  if (i>=HX711_MAX_WAIT) {
+    return luaL_error( L, "ADC timeout!", ( unsigned )0 );
+  }
+
+  for (i = 0; i<24 ; i++){  //clock in the 24 bits
+    platform_gpio_write(clk_pin,1);
+    platform_gpio_write(clk_pin,0);
+    data = data<<1;
+    if (platform_gpio_read(data_pin)==1) {
+      data = i==0 ? -1 : data|1; //signextend the first bit
+    }
+  }
+  //add 25th clock pulse to prevent protocol error (probably not needed 
+  // since we'll go to sleep immediately after and reset on wakeup.)
+  platform_gpio_write(clk_pin,1);
+  platform_gpio_write(clk_pin,0);
+  //sleep
+  platform_gpio_write(clk_pin,1);
+  lua_pushinteger( L, data );
+  return 1; 
+}
+
+#define MIN_OPT_LEVEL 2
+#include "lrodefs.h"
+const LUA_REG_TYPE hx711_map[] =
+{
+  { LSTRKEY( "init" ), LFUNCVAL( hx711_init )},
+  { LSTRKEY( "read" ), LFUNCVAL( hx711_read )},
+  { LNILKEY, LNILVAL}
+};
+
+LUALIB_API int luaopen_hx711(lua_State *L) {
+  // TODO: the below todo was inherited from the ws2812 code but is still valid.
+  // TODO: Make sure that the GPIO system is initialized
+  LREGISTER(L, "hx711", hx711_map);
+  return 1;
+}

app/modules/modules.h

@@ -245,6 +245,14 @@
 #define ROM_MODULES_TSL2561
 #endif
 
+#if defined(LUA_USE_MODULES_HX711)
+#define MODULES_HX711      "hx711"
+#define ROM_MODULES_HX711  \
+    _ROM(MODULES_HX711, luaopen_hx711, hx711_map)
+#else
+#define ROM_MODULES_HX711
+#endif
+
 #define LUA_MODULES_ROM     \
         ROM_MODULES_GPIO    \
         ROM_MODULES_PWM		\
@@ -275,6 +283,7 @@
         ROM_MODULES_RTCFIFO \
         ROM_MODULES_SNTP    \
         ROM_MODULES_BMP085  \
-        ROM_MODULES_TSL2561
+        ROM_MODULES_TSL2561 \
+        ROM_MODULES_HX711  
 
 #endif