Add README for ground node

README.md

+# Base Station
+
+The base station (BS) or ground node communicates to mobile nodes (MN) in
+several ways. The following figure shows the GN with its external connections.
+
+![Base Station](./img/ground_node.png)
+
+The BS has a receiver (Rx) to receive data emitted by mobile nodes. The Rx is
+always the same independent of the field site or purpose. The Tx can have
+different settings. It can allow for download of data or only cause MN to emit
+beacons (basically a signal where tagged animals report presence and the base
+station reports time and signal strength).  Tx boards must be programmed to the
+desired purpose. The Tx board (as shown in the figure above) is removed, it must
+be connected to the 3 pin headers (be careful not to bend pins).
+
+The hardware of the base station is split into two parts: a Raspberry Pi that
+allows the WiFi access and a STM32F04 Discovery board.
+
+## Raspberry Pi
+The Raspberry Pi runs the operating system (OS) from a micro SD card (see slot
+marked with '1' on the following figure).
+
+![Raspberry Pi](./img/raspberry_pi.png)
+
+To start the raspberry pi, connect any 12V power source to the DC-DC converter
+(e.g., car battery; this will power it for at least 3 days). Subsequently, the
+Raspberry Pi will read the operating system from a SD card and boot. This is
+indicated by a lighting red LED (see '2' in figure) and an irregularly flashing
+green LED. If the green LED is lighting permanently, the is an issue with the OS
+or the SD card is broken.
+
+The Pi will now host a WiFi hotspot using the module connected to the USB port.
+If no hotspot (called BATS x, x = ID) pops up, restart. To enable the WiFi
+access, a WiFi module must be inserted into the USB port (see '3').
+
+## Discovery Board
+Once power is supplied to the system, the Discovery board shows a flashing blue
+LED (see figure below on left side).
+
+![STM 32](./img/stm32.png)
+
+The blinking blue LED indicates that the BS has no GPS-fix, yet (for time
+synchronization). The red LEDs 1 and 2 must light and flash,
+respectively. Once the BS received a GPS fix LED 5 (orange) will light
+and the LED 4 (red) is flashing in a 1s rhythm. If the BS keeps flashing
+blue, check GPS antenna and the small cable (see base-station figure).
+
+# Software
+The software, referred to as firmware (FW) for embedded systems, is in separate
+directories; `RPi_FW` for the Raspberry Pi and `STM32F04` for the Discovery
+board.
+Both directories have separate README files
+([RPi_FW/README.md](RPi_FW/README.md),
+[STM32F04_FW/README.md](STM32F04_FW/README.md)).

STM32F04_FW/Makefile

@@ -73,7 +73,7 @@ clean:
 	find $(OBJDIR) -type f -name '*.o' -print0 | xargs -0 -r rm
 
 flash: $(OBJDIR)/$(PROJ_NAME).bin
-	/home/BjoernC/Programs/stlink/st-flash write $(OBJDIR)/$(PROJ_NAME).bin 0x8000000
+	st-flash write $(OBJDIR)/$(PROJ_NAME).bin 0x8000000
 
 # Dependdencies
 $(OBJDIR)/$(PROJ_NAME).elf: $(OBJS) | $(OBJDIR)