HAL_Linux: added qflight README.md

libraries/AP_HAL_Linux/qflight/README.md

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+# ArduPilot on Qualcomm Flight
+
+This is a port of ArduPilot to the Qualcomm Flight development board:
+
+  http://shop.intrinsyc.com/products/snapdragon-flight-dev-kit
+
+This board is interesting because it is small but offers a lot of CPU
+power and two on-board cameras.
+
+The board has 4 'Krait' ARM cores which run Linux (by default Ubuntu
+14.04 Trusty), plus 3 'Hexagon' DSP cores which run the QURT RTOS.
+
+There are two ports of ArduPilot to this board. One is called
+'HAL_QURT' and runs primarily on the DSPs, with just a small shim on
+the ARM cores. The other is a HAL_Linux subtype called 'QFLIGHT' which
+runs mostly on the ARM cores, with just sensor and UARTs on the DSPs.
+
+This is the readme for the QFLIGHT port. See the AP_HAL_QURT directory
+for information on the QURT port.
+
+# Building ArduPilot for 'QFLIGHT'
+
+Due to some rather unusual licensing terms from Intrinsyc we cannot
+distribute binaries of ArduPilot (or any program built with the
+Qualcomm libraries). So you will have to build the firmware yourself.
+
+To build ArduPilot you will need 3 library packages from
+Intrinsyc. They are:
+
+ * the HEXAGON_Tools package, tested with version 7.2.11
+ * the Hexagon_SDK packet, version 2.0
+ * the HexagonFCAddon package, tested with Flight_BSP_1.1_ES3_003.2
+
+These packages should all be unpacked in a $HOME/Qualcomm directory.
+
+To build APM:Copter you then do:
+
+```
+ cd ArduCopter
+ make qflight -j4
+```
+
+you can then upload the firmware to your board by joining to the WiFi
+network of the board and doing this
+
+```
+ make qflight_send FLIGHT_BOARD=myboard
+```
+
+where "myboard" is the hostname or IP address of your board.
+
+This will install two files:
+
+```
+ /root/ArduCopter.elf
+ /usr/share/data/adsp/libqflight_skel.so
+```
+
+To start ArduPilot just run the elf file as root on the flight
+board. You can control UART output with command line options. A
+typical startup command would be:
+
+```
+/root/ArduCopter.elf -A udp:192.168.1.255:14550:bcast -e /dev/tty-3 -B qflight:/dev/tty-2 --dsm /dev/tty-4
+```
+
+That will start ArduPilot with telemetry over UDP on port 14550, GPS
+on tty-2 on the DSPs, Skektrum satellite RC input on tty-4 and
+ESC output on tty-3.
+
+Then you can open your favourite MAVLink compatible GCS and connect
+with UDP.
+
+# Logging
+
+Logs will appear in /var/APM/logs as usual for Linux ArduPilot
+ports. You can download logs over MAVLink or transfer over WiFi.
+
+# UART connections
+
+The Qualcomm Flight board has 4 DF13 6 pin UART connectors. Be careful
+though as they do not have the same pinout as the same connectors on a
+Pixhawk.
+
+The pinout of them all is:
+
+ * pin1: power
+ * pin2: TX
+ * pin3: RX
+ * pin5: GND
+
+3 of the 4 ports provide 3.3V power on pin1, while the 4th port
+provides 5V power. Note that pin6 is not ground, unlike on a Pixhawk.
+
+The 4 ports are called /dev/tty-1, /dev/tty-2, /dev/tty-3 and
+/dev/tty-4. The first port is the one closest to the USB3
+connector. The ports proceed counter-clockwise from there. So tty-2 is
+the one closest to the power connector.
+
+Only tty-2 provides 5V power. The others provide 3.3V power. You will
+need to check whether your GPS can be powered off 3.3V.
+
+# ESC PWM Output
+
+To get signals to ESCs or servos you need to use a UART. The default
+setup is to send 4 PWM signals as serial data on /dev/tty-3. This is
+designed to work with this firmware for any ArduPilot compatible
+board:
+
+  https://github.com/tridge/ardupilot/tree/hal-qurt/libraries/RC_Channel/examples/RC_UART
+
+that firmware will read the UART serial stream and output to the PWM
+output of the board you use. For example, you could use a Pixracer or
+Pixhawk board. This is an interim solution until Qualcomm/Intrinsyc
+release an ESC add-on control board for the Qualcomm Flight.
+
+Note that you can also use RC input from that attached board, allowing
+you to use any ArduPilot compatible RC receiver.