Some usage instructions

README.md

@@ -1,10 +1,25 @@
 # STM32_RTTY
 STM32 & SI4032 rtty test
 
-Use: 
+Use:
 https://www.wyzbee.com/download/Utilities/Software/CoIDE-1.7.8.exe
 
 And:
 https://launchpad.net/gcc-arm-embedded/5.0/5-2016-q3-update/+download/gcc-arm-none-eabi-5_4-2016q3-20160926-win32.exe
 
 Have a nice day ;)
+
+# Configuration
+All configs in ```config.h```
+
+* ```CALLSIGN``` RTTY callsign
+* ```APRS_CALLSIGN``` APRS callsign
+* ```APRS_SSID``` APRS SSID - '1' -> 1, 'A' -> 10 etc.
+* ```RTTY_TO_APRS_RATIO``` number of RTTY frames between each APRS frame
+* ```RTTY_FREQUENCY``` RTTY frequency in MHz
+* ```APRS_FREQUENCY``` APRS frequency in MHz
+* ```RTTY_SPEED``` RTTY speed in bauds
+* ```RTTY_7BIT``` Use 7 bit RTTY
+* ```RTTY_USE_2_STOP_BITS``` use 2 stop bits
+* ```Smoc``` Power 0-7, where 7 means 42.95 mW@434.150 MHz measured on E4406A
+* ```tx_delay``` Delay between frames in milliseconds