add dac module

components/modules/Kconfig

@@ -74,6 +74,12 @@ config LUA_MODULE_CAN
   help
       Includes the can module.
 
+config LUA_MODULE_DAC
+  bool "DAC module"
+  default "n"
+  help
+      Includes the dac module.
+
 config LUA_MODULE_DHT
   bool "DHT11/21/22/AM2301/AM2302 module"
   default "n"

components/modules/dac.c

@@ -0,0 +1,67 @@
+// Module for interfacing with dac hardware
+
+#include <string.h>
+
+#include "module.h"
+#include "lauxlib.h"
+
+#include "driver/gpio.h"
+#include "driver/dac.h"
+
+
+#define GET_CHN(idx) \
+  int chn = luaL_checkint( L, idx ); \
+  luaL_argcheck( L, chn >= DAC_CHANNEL_1 && chn <= DAC_CHANNEL_MAX, idx, "invalid channel" );
+
+// Lua: enable( dac_channel )
+static int ldac_enable( lua_State *L )
+{
+  GET_CHN(1);
+
+  if (dac_output_enable( chn ) != ESP_OK)
+    return luaL_error( L, "dac failed" );
+
+  return 0;
+}
+
+// Lua: disable( dac_channel )
+static int ldac_disable( lua_State *L )
+{
+  GET_CHN(1);
+
+  if (dac_output_disable( chn ) != ESP_OK)
+    return luaL_error( L, "dac failed" );
+
+  return 0;
+}
+
+// Lua: write( dac_channel )
+static int ldac_write( lua_State *L )
+{
+  GET_CHN(1);
+
+  int data = luaL_checkint( L, 2 );
+  luaL_argcheck( L, data >= 0 && data <= 255, 2, "out of range" );
+
+  if (dac_output_voltage( chn, data ) != ESP_OK)
+    return luaL_error( L, "dac failed" );
+
+  return 0;
+}
+
+
+
+// Module function map
+static const LUA_REG_TYPE dac_map[] =
+{
+  { LSTRKEY( "enable" ),  LFUNCVAL( ldac_enable ) },
+  { LSTRKEY( "disable" ), LFUNCVAL( ldac_disable ) },
+  { LSTRKEY( "write" ),   LFUNCVAL( ldac_write ) },
+
+  { LSTRKEY( "CHANNEL_1" ), LNUMVAL( DAC_CHANNEL_1 ) },
+  { LSTRKEY( "CHANNEL_2" ), LNUMVAL( DAC_CHANNEL_2 ) },
+
+  { LNILKEY, LNILVAL }
+};
+
+NODEMCU_MODULE(DAC, "dac", dac_map, NULL);

docs/en/modules/dac.md

@@ -0,0 +1,69 @@
+# DAC Module
+| Since  | Origin / Contributor  | Maintainer  | Source  |
+| :----- | :-------------------- | :---------- | :------ |
+| 2018-10-14 | [Arnim Läuger](https://github.com/devsaurus) | [Arnim Läuger](https://github.com/devsaurus) | [dac.c](../../../components/modules/dac.c)|
+
+The DAC module provides access to the two built-in Digital to Analog Converters.
+
+Each DAC is assigned to a dedicated GPIO:
+- DAC channel 1 is attached to GPIO25
+- DAC channel 2 is attached to GPIO26
+
+The DACs are 8-bit, thus the output values are restricted to the range from 0 to 255.
+
+## dac.disablee()
+Disables DAC output on the related GPIO.
+
+#### Syntax
+```lua
+dac.disable(channel)
+```
+
+#### Parameters
+- `channel` DAC channel, one of
+    - `dac.CHANNEL_1`
+    - `dac.CHANNEL_2`
+
+#### Returns
+`nil`
+
+An error is thrown in case of invalid parameters or if the dac failed.
+
+
+## dac.enable()
+Enables DAC output on the related GPIO.
+
+#### Syntax
+```lua
+dac.enable(channel)
+```
+
+#### Parameters
+- `channel` DAC channel, one of
+    - `dac.CHANNEL_1`
+    - `dac.CHANNEL_2`
+
+#### Returns
+`nil`
+
+An error is thrown in case of invalid parameters or if the dac failed.
+
+
+## dac.write()
+Sets the output value of the DAC.
+
+#### Syntax
+```lua
+dac.write(channel, value)
+```
+
+#### Parameters
+- `channel` DAC channel, one of
+    - `dac.CHANNEL_1`
+    - `dac.CHANNEL_2`
+- `value` output value
+
+#### Returns
+`nil`
+
+An error is thrown in case of invalid parameters or if the dac failed.

mkdocs.yml

@@ -35,6 +35,7 @@ pages:
         - 'bit':          'en/modules/bit.md'
         - 'bthci':        'en/modules/bthci.md'
         - 'can':          'en/modules/can.md'
+        - 'dac':          'en/modules/dac.md'
         - 'dht':          'en/modules/dht.md'
         - 'encoder':      'en/modules/encoder.md'
         - 'file':         'en/modules/file.md'