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DAISY-7 - GPS/MEMS module

9 Degrees of Freedom module which integrated MEMS Accelerometer, Gyroscope, Compass, Barometer and GPS receiver in just 4x4cm.


Operating Temperature range: -30 +85 deg-C


  • Chip Skytraq Venus638LPx
  • Up to 10 reads per second
  • 65 channels
  • Tests 8 million time-frequency hypothesis per sec
  • Open sky cold start 29 second
  • Signal detection better than -161dBm
  • Accuracy 2.5m CEP
  • ~28mA in tracking and navigation mode
  • Multipath detection and suppression
  • Digital output interface type: Serial 3V3 level
  • Baudrate 115200,8,N,1 (how to change it)
  • Datasheet in PDF format

Linear accelerometer

  • Chip ST LIS331DLH
  • 3-axes linear digital accelerometer
  • Ultra low-power mode consumption down to 10µA
  • ±2g/±4g/±8g dynamically selectable full-scale
  • 16 bit data output
  • Generators for free-fall and motion detection
  • Sleep to wake-up function
  • 6D orientation detection
  • 10000g high shock survivability
  • Digital output interface type: I2C 3V3 level
  • Datasheet in PDF format


  • Chip ST L3G4200D
  • Ultra-stable three-axis
  • Three selectable full scales (250/500/2000 dps)
  • 16 bit-rate value data output
  • 8-bit temperature data output
  • Integrated low- and high-pass filters with userselectable bandwidth
  • Ultra-stable over temperature and time
  • Embedded power-down and sleep mode
  • Embedded temperature sensor
  • Embedded FIFO
  • High shock survivability
  • Digital output interface type: I2C 3V3 level
  • Datasheet in PDF format


  • Chip Honeywell HMC5883L
  • 3-Axis Magnetoresistive Sensors and ASIC in a 3.0x3.0x0.9mm LCC Surface Mount Package
  • 12-Bit ADC Coupled with Low Noise
  • AMR Sensors Achieves 5 milli-gauss
  • Resolution in ±8 Gauss Fields
  • Enables 1° to 2° Degree Compass Heading Accuracy
  • Low Power Consumption (100µA)
  • Wide Magnetic Field Range (±8Oe)
  • Sensors Can Be Used in Strong Magnetic Field Environments with a 1° to 2° Degree Compass Heading Accuracy
  • Fast 160 Hz Maximum Output Rate
  • Digital output interface type: I2C 3V3 level
  • Datasheet in PDF format


  • Chip Bosch BMP085
  • Pressure range: 300 ... 1100hPa (+9000m ... -500m above sea level)
  • Low power: 5µA at 1 sample/sec. in standard mode
  • Low noise:
    • 0.06hPa (0.5m) in ultra low power mode
    • 0.03hPa (0.25m) ultra high resolution mode
    • down to 0.1m (rms noise) possible
  • Digital output interface type: I2C 3V3 level
  • Datasheet in PDF format

Pinout on Daisy connector J2

Pin # Signal Direction Description
1 3V3 Power supply 3.3 Volt
2 TXD I Cpu TXD serial line wired to GPS RX line
3 RXD O Cpu RXD serial line wired to GPS TX line
4 NC Not connected
5 NC Not connected
6 NC Not connected
9 NC Not connected
10 GND Power supply GND

The I2C bus is wired to the Compass, Accelerometer, Gyroscope and Barometer chips.

Fore more details please refere to the schematic.


These are the usable connectors where to plug this board using the factory default Linux image:

Daisy connector Serial device I2C device
FOX Board G20 (+Daisy-1) D1 /dev/ttyS2 /dev/i2c-0
FOX Board G20 (+Daisy-1) D6 /dev/ttyS4 /dev/i2c-0
FOX Board G20 (+Daisy-1) D8 /dev/ttyS3 /dev/i2c-0
TERRA D10 /dev/ttyS4 /dev/i2c-0

Basic code examples

Following are some examples of code in Python to read the data from the chip mounted on the DAISY-7 using a FOX Board G20 or a Terra Board.

They use Daisy classes defined inside the the Acme Systems ablib.py.

Read NMEA messages from the GPS chip

This example reads the NMEA message send by the GPS chip on the /dev/ttyS4 serial port (FOX.D6 or TERRA.D10 daisy connectors) and shows them on the Linux command line.


Run it by typing:

~/playground/python/daisy7# python readNMEA.py

Get the GPS coordinates and show the current position on Google maps

This example filters the NMEA messages GGA - Global Positioning Systems Fix Data and shows the Latitute and Longitude value on the system console provideing an URL to see on Google maps the current GPS position.


Run it by typing:

~/playground/python/daisy7# python googleCoordinates.py 
     Latitude:  41.9654233333
    Longitude:  12.07834
          URL: https://maps.google.com/maps?q=41.965423,12.078340

     Latitude:  41.9654233333
    Longitude:  12.07834
          URL: https://maps.google.com/maps?q=41.965423,12.078340

     Latitude:  41.9654233333
    Longitude:  12.07834
          URL: https://maps.google.com/maps?q=41.965423,12.078340

Insert URL value on your browser and shown where the Daisy-7 is:

Read the Accelerometer chip

This example reads the X,Y and Z axis linear accelleration via I2C bus.


Run the example then move the DAISY-7 board so see linear speed variations.

~/playground/python/daisy7# python acc.py
X=  1216 Y=-16528 Z= -2992
X=  1200 Y=-16272 Z= -2944
X=  1136 Y=-16288 Z= -3024
X=  1184 Y=-16272 Z= -2976
X=  1184 Y=-16304 Z= -2992
X=  1168 Y=-16352 Z= -2976

Read the Gyroscope chip

This example reads the X,Y and Z axis angular speed from the gyroscope chip via I2C bus.


Run the example then move the DAISY-7 board so see angular speed variations.

~/playground/python/daisy7# python gyro.py
X=   -10 Y=   -18 Z=     8
X=   -13 Y=   -17 Z=     8
X=    -2 Y=   -16 Z=     6
X=    -8 Y=   -18 Z=     7
X=    -7 Y=   -18 Z=     8
X=   -36 Y=   -18 Z=    14

Read the Compass chip

To read the Honeywell HMC5883L compass chip we have integrated in the ablib library part of the Think Bowl I2C Python Library.

Some features of this library are:

This is an example of code to use them:


~/playground/python/daisy7# python compass.py
X=  -147 Y=  -184 Z=  -437
X=  -215 Y=  -314 Z=  -375
X=    57 Y=  -292 Z=  -420
X=   138 Y=  -222 Z=  -427
X=   315 Y=  -128 Z=  -353

Read the Barometer chip registers via I2C bus


Hardware reference

How to change the GPS baudrate

The serial speed of GPS chip is fixed by hardware using the pin BAUD_SEL0 and BAUD_SEL1 visible on the schematic of GPS section. These pin are set at 3V3 via R19 and R17 resistors. R20 and R18 are Not Mounted.

This is the table of the serial speeds we can set changing the state of these pins:

Speed BAUD_SEL0 BAUD_SEL1 R17 R18 R19 R20
4800 1 0 No Yes Yes No
9600 0 0 No Yes No Yes
38400 0 1 Yes No No Yes
115200 1 1 Yes No Yes No

Third party projects


DAISY-7 : GPS-MEMS daisy module EURO 79.00

Daisy-7 is a 9 Degrees of Freedom module (9DOF) with digital MEMS (accelerometer, gyroscope, compass, barometer) and a GPS receiver IC in just 4x4cm.

Note: the daisy flat cable to wire this board is not included. Don't forget to buy it (code FLAT-20CM)

| Product description | Daisy catalog |

GPSANT : GPS active antenna EURO 12.00

GPS active antenna with SMA male connector to use Daisy-7 add-on board.

FLAT-20CM : 20cm flat cable with sockets for Daisy wiring EURO 3.00

20 cm ribbon cable with 10 wires compatible with the Acme Daisy Cabling System.

At least one of these cables is required to connect each Daisy module.

if you need different lengths please consider making your own the cable using the IDC socket JJ-02291-10P-F and the flat cable FC-3754-1M.

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P.IVA/C.F. 08114831004
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PEC: acmesystemssrl@pec.it
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Acme Systems provides this documentation "as is" without warranty or guarantees of any kind. We not provide any direct support for the Open Source preinstalled software but, through these pages and forum posts, all of the information required to obtain the sources, install, use and update the Open Source software that can be run on the Acme boards. Please note that all of the preinstalled software, used on the Acme Systems products, are Open Source so you have to check the license terms provided by the authors (usually the GPL) before using it in any commercial or non-commercial product, by yourself. Before to contact us please note that WE ARE MAINLY HARDWARE DESIGNERS and NOT LINUX GURUS and therefore could be better to post your questions to the Acme Systems forum and ensure that all of the site contributors and large software community can read and reply to your questions.

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