Merge pull request #394 from AvSquirrel/gps-uart-fix

GPS UART fix for RPi 3. Fixes #393.

image/config.txt

@@ -5,3 +5,6 @@ max_usb_current=1
 dtparam=i2c1=on
 dtparam=i2c1_baudrate=400000
 dtparam=i2c_arm_baudrate=400000
+
+# move RPi3 Bluetooth off of hardware UART to free up connection for GPS
+dtoverlay=pi3-miniuart-bt

main/ry835ai.go

@@ -136,9 +136,9 @@ func initGPSSerial() bool {
 		device = "/dev/ttyUSB0"
 	} else if _, err := os.Stat("/dev/ttyACM0"); err == nil {
 		device = "/dev/ttyACM0"
-	} else if _, err := os.Stat("/dev/ttyS0"); err == nil {
+		//} else if _, err := os.Stat("/dev/ttyS0"); err == nil { // ttyS0 appears to be mini UART on RPi 3
-		device = "/dev/ttyS0"
+		//	device = "/dev/ttyS0"
-	} else if _, err := os.Stat("/dev/ttyAMA0"); err == nil {
+	} else if _, err := os.Stat("/dev/ttyAMA0"); err == nil { // ttyAMA0 is PL011 UART (GPIO pins 8 and 10) on all RPi
 		device = "/dev/ttyAMA0"
 	} else {
 		log.Printf("No suitable device found.\n")

test/mtk_config.sh

@@ -0,0 +1,73 @@
+#!/bin/bash
+#
+# mtk_config.sh: Script to set up MTK3339 receiver for Stratux. 
+# Resets receiver to 9600 and 1 Hz GPRMC messaging, then enables 
+# WAAS, 5 Hz position reporting, the NMEA messages needed by
+# Stratux, and 38400 bps serial output.
+
+printf "About to configure MTK3339 receiver on /dev/ttyAMA0.\n"
+printf "Press ctrl-C to abort or any other key to continue.\n"
+read
+
+# Iterate through common bitrates and send commands to reduce output to 1 Hz / 9600 bps.
+printf "Setting MTK and RPi baud rate of /dev/ttyAMA0 to 9600. Iterating through common rates.\n"
+printf "Current /dev/ttyAMA0 baudrate.\n"
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+printf "\$PMTK251,9600*17\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "38400 bps.\n"
+stty -F /dev/ttyAMA0 38400
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+printf "\$PMTK251,9600*17\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "115200 bps.\n"
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+stty -F /dev/ttyAMA0 115200
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+printf "\$PMTK251,9600*17\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "57600 bps.\n"
+stty -F /dev/ttyAMA0 57600
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+printf "\$PMTK251,9600*17\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "19200 bps.\n"
+stty -F /dev/ttyAMA0 19200
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+printf "\$PMTK251,9600*17\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "4800 bps.\n"
+stty -F /dev/ttyAMA0 4800
+printf "\$PMTK220,1000*1F\r\n" > /dev/ttyAMA0
+printf "\$PMTK251,9600*17\r\n" > /dev/ttyAMA0
+sleep 0.2
+
+
+stty -F /dev/ttyAMA0 9600
+printf "\$PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29\r\n" > /dev/ttyAMA0
+
+printf "MTK has been set to 9600 baud with RMC messages at 1 Hz.\n"
+printf "Press ctrl-C to abort, or any other key enter to continue with setup.\n"
+read
+
+# Now start the Stratux setup.
+printf "Sending MTK command to set GPS baud rate to 38400\n"
+printf "\$PMTK251,38400*27\r\n" > /dev/ttyAMA0
+
+printf "Setting RPi baud rate of /dev/ttyAMA0 to 38400\n"
+stty -F /dev/ttyAMA0 38400
+sleep 0.2
+printf "Sending MTK command to configure NMEA message output\n"
+printf "\$PMTK314,0,1,1,1,5,5,0,0,0,0,0,0,0,0,0,0,0,0,0*29\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "Sending MTK commands to enable WAAS\n"
+printf "\$PMTK301,2*2E\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "\$PMTK513,1*28\r\n" > /dev/ttyAMA0
+sleep 0.2
+printf "Sending MTK commands to enable 5 Hz position reporting\n"
+printf "\$PMTK220,200*2C\r\n" > /dev/ttyAMA0
+
+# Finally, test the connection.
+printf "Opening /dev/ttyAMA0 to listen to GPS. Press ctrl-C to cancel.\n"
+cat /dev/ttyAMA0