The accelerometer outputs a triple analog signal concerning the detected acceleration on each of the axes, and the signals are available at pin 4 for the X axis, 3 for the Y axis and 2 for the Z axis.īy the JREF jumper is possible to connect Arduino’s VREF to 3.3 V, so that the 1.65 V accelerometer output, that corresponds to no acceleration (0g), roughly coincides with the 512 value at the output of the A/D 10-bit Arduino converter, ie in the middle of the excursion (the A / D ranges from 0 to 1024). This module is powered with 3.3V by the Arduino board by using the the 3.3V line and GND, which on the MMA7361 reach the pins, respectively, VCC and GND. The accelerometer, dubbed ACC in the wiring diagram: it’s the MMA7361, a three axes one produced by Freescale: for this we use the version produced by Sparkfun, already mounted on a board showing 9-pins single-in-line with a 2.54mm pitch. You can access a FAT16 or FAT32 formatted microSD, by using the SD Arduino library available in the development environment, taking care of using SD.begin(4) to configure the Chip Select different from the standard. The signals are connected to the ICSP header so as to allow compatibility with the Arduino MEGA.
#Old royaltek gps data loger serial#
The GPS module is activated by setting pin 7 to logic low: from that moment it will cyclically transmit NMEA strings on the serial port until it will be disabled by setting it to high.Īs for the microSD slot, the shield includes 74HC4050D level converter to allow communication via the SPI at 0/3, 3V levels (in fact the SD card and micro SD use the Serial Peripheral Interface bus for external communications). In this regard it should be noted that lines 0 and 1 constitute Arduino’s physical UART: if this is not available because it is already used by other applications (for example because you mounted another shield), you can, via the SoftwareSerial library, set your board to handle 5 and 6 lines as a virtual UART. This signal is available on the serial and GPS connector through GPSRX and GPSTX jumpers and can be routed to pins 0 and 1 (RX and TX of the integrated serial port) of the Arduino.
Communication is serial (4800 bps) and uses the TX and RX lines at TTL level.
The main part of the shield is obviously composed of the GlobalSat GPS EM406 module, with a built-in antenna (on top of it) which communicates with the Arduino via the NMEA 0183 protocol. Moreover, we have the 40 mA of the Arduino ONE, for a total of 75 mA in LOG mode (ie during the acquisition and recording of coordinates) and 45 mA in standby mode. Our measures, when powering it with the Arduino 5V, indicate a consumption of around 35 mA, with the GPS on, reduced to about 5 mA by turning it off via pin 7. Let’s look at the circuit of the shield, which, by virtue of its reduced power consumption, it is powered directly from the Arduino. This can be useful if you plan to mount more shields above the circuit, which inevitably disturb the reception of satellites signals. The GPS receiver is connected through two connectors (each one alternative to the other) then you can actually place it out of the shield. This feature was obtained thanks to an accelerometer which, in addition to stop saving data when the tracker has stopped, also allows to turn off the GPS module to reduce consumption, which is useful, since this kind of systems normally feeds on batteries.Īs said, the logger consists of a shield, on which there are mainly the GPS receiver, the SD-Card reader and the accelerometer, in addition to an Arduino UNO board. For this reason we decided to implement a system that is able to stop recording when the logger is still.
This means consuming memory because the device continuously saves almost the same position. Being experienced users of other loggers in the market, we realized that one of the most annoying things is to forget to turn it off once you get to destination.