Software and basic procedures for altimeter operation
Figure 1: Bread Board layou
Here you can download the Arduino sketch firmware for your just build barometric altimeter.
Used absolute pressure sensor is a SCP1000, you can download the datasheet here, this sensor have a digital SPI interface and a range of 30 kPa-120 kPa.
This sensor can be incorporated in a ground station, it have an embedded temperature sensor that, accuracy apart, can be useful to experiment with compensation procedures.
Hardware is composed by an 3.3 V Arduino Pro running at 8 Mhz and an 3.3V SCP1000 breakout board.
Wiring is straightforward, refer to the Figure 1 Fritzing file can be downloaded here. To access the board you need a USB to 3.3V serial adapter, the same adapter used to program Arduino pro.
Picture 2: Wiring scheme
The final circuit hardware complexity is low so there is no need at all for an adapter PCB, if you plan to use the circuit for a long time simply sold the wires to Arduino board. The wiring scheme on Figure 2 with six M/F wires you will get a working prototype, in the picture a 90° bend header pin row have been soldered to SCP breadboard.
Figure 3: Direct wiring, with serial FTDI interface at 3,3V
Figure 4: Arduino altimeter boxed and ready to be connected to a ground station PC
If you want a rugged solution, put your board into a slotted plastic box (Figure 4); this setup is comfortable for a base station, RC/FPV/UAV setup. In the case the over all dimensions are an issue just consider to weld the SCP board to an Arduino pro mini board (Figure 5). After the wiring is done just upload the code and monitor the serial port at 9600 baud 8N1. You should get an output similar to those here reported:
<<
Initialization sea level Temperature C 16.2
Initialization sea level pressure Pa 99802
Sea level pressure from weather service Pa 99700
…
Raw pressure Pa 99182
Filtered pressure Pa 99180
Temperature C 15
Barometric altitude according, ISA m 185.5505676269
Barometric altitude corrected for pressure at sea level, m 44.2671127319
Barometric altitude corrected, current altitude and temperature known m 53.4413719177
…
Raw pressure Pa 99185
Filtered pressure Pa 99181
Temperature C 15
Barometric altitude according, ISA m 185.4594726562
Barometric altitude corrected for pressure at sea level, m 44.1800498962
Barometric altitude corrected, current altitude and temperature known m 53.354980468
…
>>
Figure 5: Arduino pro mini vs SCP1000 breakboard dimensions