document SPI and bitmap

README.md

@@ -346,24 +346,50 @@ The integration in nodemcu is developed for SSD1306 based display attached via t
 U8glib v1.17
 
 #####I2C connection
-Hook up SDA and SCL to any free GPIOs. Eg. [lua_examples/graphics_test.lua](https://github.com/devsaurus/nodemcu-firmware/blob/dev/lua_examples/graphics_test.lua) expects SDA=5 (GPIO14) and SCL=6 (GPIO12). They are used to set up nodemcu's I2C driver before accessing the display:
+Hook up SDA and SCL to any free GPIOs. Eg. `lua_examples/u8glib/graphics_test.lua` expects SDA=5 (GPIO14) and SCL=6 (GPIO12). They are used to set up nodemcu's I2C driver before accessing the display:
 ```lua
 sda = 5
 scl = 6
 i2c.setup(0, sda, scl, i2c.SLOW)
 ```
 
+#####SPI connection
+The HSPI module is used, so certain pins are fixed:
+* HSPI CLK  = GPIO14
+* HSPI MOSI = GPIO13
+* HPSI MISO = GPIO12 (not used)
+
+All other pins can be assigned to any available GPIO:
+* CS
+* D/C
+* RES (optional)
+
+Also refer to the initialization sequence eg in `lua_examples/u8glib/graphics_test.lua`:
+```lua
+spi.setup(1, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, spi.DATABITS_8, 0)
+```
+
+
 #####Library usage
-The Lua bindings for this library closely follow u8glib's object oriented C++ API. Based on the u8g class, you create an object for your display type:
+The Lua bindings for this library closely follow u8glib's object oriented C++ API. Based on the u8g class, you create an object for your display type.
+
+SSD1306 via I2C:
 ```lua
 sla = 0x3c
 disp = u8g.ssd1306_128x64_i2c(sla)
 ```
+SSD1306 via SPI:
+```lua
+cs = 8 -- GPIO15, pull-down 10k to GND
+dc = 4 -- GPIO2
+disp = u8g.ssd1306_128x64_spi(cs, dc)
+```
+
 This object provides all of u8glib's methods to control the display.
-Again, refer to [lua_examples/graphics_test.lua](https://github.com/devsaurus/nodemcu-firmware/blob/dev/lua_examples/u8g_graphics_test.lua) to get an impression how this is achieved with Lua code. Visit the [u8glib homepage](https://code.google.com/p/u8glib/) for technical details.
+Again, refer to `lua_examples/u8glib/graphics_test.lua` to get an impression how this is achieved with Lua code. Visit the [u8glib homepage](https://code.google.com/p/u8glib/) for technical details.
 
 #####Fonts
-u8glib comes with a wide range of fonts for small displays. Since they need to be compiled into the firmware image, you'd need to include them in [app/include/user_config.h](https://github.com/devsaurus/nodemcu-firmware/blob/dev/app/include/user_config.h) and recompile. Simply add the desired fonts to the font table:
+u8glib comes with a wide range of fonts for small displays. Since they need to be compiled into the firmware image, you'd need to include them in `app/include/user_config.h` and recompile. Simply add the desired fonts to the font table:
 ```c
 #define U8G_FONT_TABLE \
     U8G_FONT_TABLE_ENTRY(font_6x10)  \
@@ -371,6 +397,9 @@ u8glib comes with a wide range of fonts for small displays. Since they need to b
 ```
 They'll be available as `u8g.<font_name>` in Lua.
 
+#####Bitmaps
+Bitmaps and XBMs are supplied as strings to `drawBitmap()` and `drawXBM()`. This off-loads all data handling from the u8g module to generic methods for binary files. See `lua_examples/u8glib/u8g_bitmaps.lua`. Binary files can be uploaded with [nodemcu-uploader.py](https://github.com/kmpm/nodemcu-uploader).
+
 #####Unimplemented functions
 - [ ] Cursor handling
   - [ ] disableCursor()
@@ -379,12 +408,7 @@ They'll be available as `u8g.<font_name>` in Lua.
   - [ ] setCursorFont()
   - [ ] setCursorPos()
   - [ ] setCursorStyle()
-- [x] Bitmaps
-  - [x] drawBitmap()
-  - [x] drawXBM()
 - [ ] General functions
-  - [x] begin()
-  - [ ] print()
   - [ ] setContrast()
   - [ ] setPrintPos()
   - [ ] setHardwareBackup()