update README

README.md

@@ -39,6 +39,9 @@ Research for each of does modules has to be done
 * ESP for wifi access
 
 
+## API
+
+
 ### research
 
 #### cost estimation
@@ -103,3 +106,54 @@ Although it is long-range, it is impossible to extend the distance or get over g
 
 arduino and nixos. to let arduino access serial device it seems like the user should be added to the 'dialout' group
 
+## STM32
+
+### debugging
+#### start debugging server
+allow access to usb device (this is bad practice but works for now):
+
+``` shell
+sudo chmod 777 /dev/bus/usb/001/003
+```
+
+start gdb server:
+
+``` shell
+st-util
+```
+
+#### connect to uart
+
+``` shell
+stty -F /dev/ttyUSB0 #get baudrate
+screen /dev/ttyUSB0 9600 #set baudrate according to stty cmd
+```
+
+#### GPS NMEA Example:
+[online decoder](https://rl.se/gprmc)
+
+sample:
+
+``` shell
+$GPGSV,4,4,13,32,13,043,18*46
+$GPGLL,5103.74732,N,01345.18897,E,225640.00,A,A*60
+$GPRMC,225641.00,A,5103.74725,N,01345.18895,E,0.879,,270223,,,A*7C
+$GPVTG,,T,,M,0.879,N,1.629,K,A*29
+$GPGGA,225641.00,5103.74725,N,01345.18895,E,1,04,8.27,90.8,M,43.6,M,,*69
+$GPGSA,A,3,01,21,04,03,,,,,,,,,15.97,8.27,13.66*02
+$GPGSV,4,1,13,01,70,140,30,03,73,277,20,04,30,197,25,06,02,306,*77
+$GPGSV,4,2,13,09,00,2114,3,13,21,46,141,17,22,39,056,,28,26,074,07,31,24,084,15*70
+$GPGSV,4,4,13,32,13,043,17*49
+$GPGLL,5103.74725,N,01345.18895,E,225641.00,A,A*65
+$GPGSV,4,4,13,32,13,043,17*49
+$GPGLL,5103.74725,N,01345.18895,E,225641.00,A,A*65
+$GPRMC,225642.00,A,5103.74732,N,01345.18880,E,0.748,,270223,,,A*70
+$GPVTG,,T,,M,0.748,N,1.385,K,A*27
+$GPGGA,225642.00,5103.74732,N,01345.18880,E,1,04,8.27,90.9,M,43.6,M,,*69
+$GPGSA,A,3,01,21,04,03,,,,,,,,,15.96,8.27,13.65*00
+$GPGSV,4,1,13,01,70,140,29,03,73,277,21,04,30,197,25,06,02,306,*7E
+$GPGSV,4,2,13,09,00,2114,3,13,21,46,141,17,22,39,056,,28,26,074,07,31,24,084,13*76
+
+```
+
+`