additional changes

README.md

@@ -17,6 +17,8 @@ Please see the various Makefile's included in the project for more information.
 
 To build the firmware, use the ```make``` command, followed by -f and the correct makefile, followed by the type of board you are using. 
 
+> **_NOTE:_**  The only two known tested targets are ```mmdvm-hs-hat-dual``` and ```mmdvm-hs-hat-dual-usb```.
+
 An example of this would be ```make -f Makefile.STM32FX mmdvm-hs-hat-dual``` for a full duplex modem hotspot, attached to GPIO.
 
 ## Firmware installation
@@ -25,6 +27,28 @@ The device can be used on top on a RPi attached via the GPIO port or standalone
 
 The USB connection requires firmware with bootloader support whereas the GPIO version does not. For USB connection a bootloader has to be installed initally. This requires STlink connection. After that is done the firmware upgrade can be done via the USB connection. The STlink connection can be used as fallback if wrongly configured firmware was installed for example.
 
+### Install the firmware via GPIO on Raspberry Pi
+
+> **_NOTE:_**  Your mileage may vary with these instructions, the hotspot boards are loosely designed around a common factor but not all are created equally.
+
+First you will need to disable the serial console and disable bluetooth. Edit ```/boot/cmdline.txt``` and remove the line ```console=serial0, 115200```.
+Next, you will need to disable bluetooth on the board. Edit ```/boot/config.txt``` and add a line containing ```dtoverlay=disable-bt```. Reboot.
+
+> Most sets of instructions reccomend to download stm32flash from online, however we have found the prepackaged version to work fine.
+
+Once the hotspot is back on, navigate to the build folder where you compiled the firmware. Put a jumper across the J1 points on the board, and the RED heartbeat LED should stop flashing. Run the below command to flash.
+
+```stm32flash -v -w dvm-firmware-hs_f1.bin -i 20,-21,21,-20 -R /dev/ttyAMA0```
+
+You should see the below output if the board flashed successfully.
+```
+Wrote and verified address 0x0800be40 (100.00%) Done.
+
+Resetting device... 
+Reset done.
+```
+
+
 ### Install the firmware with bootloader support for USB connection
 
 If you want to use the device via USB port you have to install a bootloader and build the firmware with bootloader support. As the raw device cannot be used with USB you have to use a USB-serial adapter or STlink device.