Merge pull request #919 from christakahashi/newdocs-hx711

docs for hx711

docs/en/modules/hx711.md

@@ -0,0 +1,48 @@
+# HX711 Module
+
+This module provides access to an HX711 load cell amplifier/ADC.  The HX711 is an inexpensive 24bit ADC with programmable 128x, 64x, and 32x gain.  Currently only channel A at 128x gain is supported.
+
+Note: To save ROM image space, the hx711 module is not compiled into the firmware by default.
+
+
+## hx711.init()
+
+Initialize io pins for hx711 clock and data.
+
+#### Syntax
+`hx711.init(clk,data)`
+
+#### Parameters
+- `clk` pin the hx711 clock signal is connected to.
+- `data` pin the hx711 data signal is connected to.
+
+#### Returns
+`nil`
+
+#### Example
+```lua
+-- Initialize the hx711 with clk on pin 5 and data on pin 6
+hx711.init(5,6)
+```
+## hx711.read()
+
+Read digital loadcell ADC value.
+
+#### Syntax
+`hx711.read(mode)`
+
+#### Parameters
+- `mode` ADC mode.  This parameter is currently ignored and reserved to ensure backward compatability if support for additional modes is added.  Currently only channel A @ 128 gain is supported.
+
+|mode | channel | gain |
+|-----|---------|------|
+| 0   | A       | 128  |
+
+#### Returns
+a number (24 bit signed ADC value extended to the machine int size.)
+
+#### Example
+```lua
+-- Read ch A with 128 gain.
+raw_data = hx711.read(0)
+```