This week’s featured photo is Andrew D2010’s in-progress GPS clock. He writes:
This shot shows an Adafruit Ultimate GPS (MTK3339), an Adafruit Temperature + Barometric Pressure Sensor (BMP085), a Itead rotary encoder (push button with 20 points), a DealExtreme J12865 (SKU 121820 with ST7920 controller) and an Arduino Uno.
I need to get this bunch of parts into a case so I can move it around easily and get on with programming it. Clever people will have notice my dodgy stacking of pins/connectors.
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Adafruit Ultimate GPS Breakout – 66 channel w/10 Hz updates [MTK3339 chipset]. We carry a few different GPS modules here in the Adafruit shop, but none that satisfied our every desire – that’s why we designed this little GPS breakout board. We believe this is the Ultimate GPS module, so we named it that. It’s got everything you want and more, with -165 dBm sensitivity, 5V friendly design, breadboard friendly, mounting holes, 10 Hz updates, 66 channels, RTC battery-compatible and has a status LED all for under $40! The newest version we carry (using the MTK3339 chipset, as of March 26th) adds built in datalogging capability and high altitude functionality with even lower power.
The breakout is built around the MTK3339 chipset, a no-nonsense, high-quality GPS module that can track up to 22 satellites on 66 channels, has an excellent high-sensitivity receiver (-165 dB tracking!), and a built in antenna. It can do up to 10 location updates a second for high speed, high sensitivity logging or tracking. Power usage is incredibly low, only 20 mA during navigation.
Best of all, we added all the extra goodies you could ever want: a ultra-low dropout 3.3V regulator so you can power it with 3.3-5VDC in, 5V level safe inputs, ENABLE pin so you can turn off the module using any microcontroller pin or switch, a footprint for optional CR1220 coin cell to keep the RTC running and allow warm starts and a tiny bright red LED. The LED blinks at about 1Hz while it’s searching for satellites and blinks once every 15 seconds when a fix is found to conserve power. If you want to have an LED on all the time, we also provide the FIX signal out on a pin so you can put an external LED on.
Two things that really stand out about the new MTK3339-based module is the high-altitude functionality and the the built in data-logging capability. Most modules permit NMEA output only when the module is traveling under 515 mph AND when its at an altitude of under 60,000 ft (18,000 m). This is to prevent the modules from being used for military use. However, as the requirements are not as strict, we’ve requested the factory to keep the speed limit but remove the altitude restriction. We trust that the factory has removed the limit but we have not done independent verification yet. If this feature is critical, please do not purchase until we’ve personally verified it!
The other cool feature of the new MTK3339-based module (which we have tested with great success) is the built in datalogging ability. Since there is a microcontroller inside the module, with some empty FLASH memory, the newest firmware now allows sending commands to do internal logging to that FLASH. The only thing is that you do need to have a microcontroller send the “Start Logging” command. However, after that message is sent, the microcontroller can go to sleep and does not need to wake up to talk to the GPS anymore to reduce power consumption. The time, date, longitude, latitude, and height is logged every 15 seconds and only when there is a fix. The internal FLASH can store about 16 hours of data, it will automatically append data so you don’t have to worry about accidentally losing data if power is lost. It is not possible to change what is logged and how often, as its hardcoded into the module but we found that this arrangement covers many of the most common GPS datalogging requirements.
Comes with one fully assembled and tested module, a piece of header you can solder to it for breadboarding, and a CR1220 coin cell holder. A CR1220 coin cell is not included, but we have them in the shop if you’d like to use the GPS’s RTC
Get started in a jiffy: wire up 3-5VDC to the VIN pin, GND is common ground, and listen on the TX pin for 9600 baud data. Then run our example sketch which will allow you to quickly set the update rate and select which NMEA sentences you want to have spit out. We will have example sketches for using the internal logging system shortly, please hold on while we clean it up!
- Satellites: 22 tracking, 66 searching
- Patch Antenna Size: 15mm x 15mm x 4mm
- Update rate: 1 to 10 Hz
- Position Accuracy: 1.8 meters
- Velocity Accuracy: 0.1 meters/s
- Warm/cold start: 34 seconds
- Acquisition sensitivity: -145 dBm
- Tracking sensitivity: -165 dBm
- Maximum Altitude for MTK3329: 18,000 meters
- Maximum Altitude for MTK3339: no limit
- Maximum Velocity: 515m/s
- Vin range: 3.0-5.5VDC
- MTK3329 Operating current: 48mA tracking, 37 mA current draw during navigation
- MTK3339 Operating current: 25mA tracking, 20 mA current draw during navigation
- Output: NMEA 0183, 9600 baud default
- DGPS/WAAS/EGNOS supported
- FCC E911 compliance and AGPS support (Offline mode : EPO valid up to 14 days )
- Up to 210 PRN channels
- Jammer detection and reduction
- Multi-path detection and compensation
Breakout board details:
- Weight (not including coin cell or holder): 8.5g
- Dimensions (not including coin cell or holder): 23mm x 35mm x 8mm / 0.9″ x 1.35″ x 0.3″