Revision as of 19:07, 11 March 2014

Using GPS module with Debian Wheezy

Vayu -2GP-A cape , Vayu-3GHP-A, Vayu-3GCP-A and Vayu-P cape come with a GPS module.

It has following interfaces with available to user and connecting to Beaglebone Black :

1. UART4 (/dev/ttyO4) : It is used for reading the GPS NMEA messages from UART port of GPS module. It should be configured for use at baud rate 19200 raw after ttyO4 has been enabled in the kernel by applying device tree overlay for UART4.

2. GPIO50 : It is used for resetting the GPS modules. It should be pulled high all the time.

3. GPIO27 : It is used as an input GPIO to receive 1 PPS output from the GPS module.

4. Switch S3 on Cape : It is push button Reset switch. To reset the module , push this button for atleast 1s or set the reset GPIO50 low for atleast 1s.

5. LED D5 on Cape : It is GPS fix LED of the GPS Module. When the Module has acquired GPS fix, this LED starts blinking at 1s OFF/1s ON . Also 1PPS output can be detected at GPIO27 after that.

6. LED D7 on Cape : It is 3.3V power Led for cape, also indicating that it should be always glowing for the GPS module to be powered on.

Connect the GPS antenna at SMA connector P6 and place the antenna under open sky for better operations and Boot up Beaglebone Black with cape mounted on it. Notice LED D7 powering up.

Depending on the GPS module had a cold start , warm start or hot start , You should soon see LED D5 to start blinking, denoting that GPS Fix has been acquired.

To read the NMEA messages from the GPS Module on Beaglebone Black :

Step 1 : Enable UART4 (/dev/ttyO4) in device tree kernel.

cd /lib/firmware

echo BB-UART4 > /sys/devices/bone_capemgr.9/slots

You can read the slots or use dmesg to see that UART4 has been enabled.

cat /sys/devices/bone_capemgr.9/slots

Output will be like this :

0: 54:PF---

1: 55:PF---

2: 56:PF---

3: 57:PF---

4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G

5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI

7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART4

Step 2 : Install Minicom or use the following commands to see NMEA messages

apt-get install minicom

minicom –s (port settings /dev/ttyO4 19200 8N1 )

or

stty –F /dev/ttyO4 19200 raw

cat /dev/ttyO4

For more information and detailed guide on Time synchronization and GPS Location , please refer to the following :

http://www.yantrr.com/wiki/Configuring_for_GPS_Location_and_Time_Synchronization