Nuts and Volts - May/June 2018

configure the Pi to use the PCB. By the way, in Python, the hash mark, or indicates a comment:

GPIO.setup(16,GPIO.OUT) SD Card Safe
to remove indicator LED
GPIO.setup(26,GPIO.IN,pull_up_down=GPIO.PUD_UP)
# Flight Mode Switch go into flight mode
GPIO.setup(23,GPIO.OUT) Flight Mode
Indicator LED
 GPIO.setup(25,GPIO.OUT) Signal
 PICAXE to start/stop collecting data
 GPIO.setup(12.GPIO.OUT) PWM IO
 pwm=GPIO.PWM(12,50) configure to
 produce 50 Hz signal for servo
 GPIO.setup(13.GPIO.OUT) PWM IO
 pwm=GPIO.PWM(13,50) configure to
 produce 50 Hz signal for servo
import RPi.GPIO as GPIO make the
GPIO available to the Pi
import smbus so the Pi can use
I2C commands
import serial so the Pi
can read GPS sentences
from picamera import PiCamera #so the Pi can
use its camera
 
 
ser = serial.Serial(port=’/dev/
ttyAMA0’,baudrate=4800,parity=serial.
PARITY_NONE,stopbits=serial.STOPBITS_
ONE,bytesize=serial.EIGHTBITS,timeout=2)

I haven’t tested all the ports in the Raspberry Pi flight computer yet. However, I still want to briefly mention them. GPIO pins 17, 22, 24, and 27 form an expansion port that also provides 3. 3 volts and ground. The second I2C pins and the SPI pins are available in four- and six-pin ports, respectively, that include 3.3V and ground.

GPIO.setwarnings(False) suppress
error messages
GPIO.setmode(GPIO.BCM) makes the Pi use
the I/O’s Broadcom names

Making the Raspberry Pi flight computer has been a real learning experience, and I’ve barely scratched the surface. I still need to run all the code I’ve written in a full test. I need to find out how to copy the code and data from the SD card to my PC, so I can analyze it in Excel.

Next are the GPIO found on the expansion board, their functions, and the Python commands used to set them up: I need to identify an appropriate power pack (cell phone back-up battery?) to operate the flight computer for its three hour balloon flight. I need to learn how to configure the Pi to start the flight code without me telling it to do so over a keyboard and monitor. Plus, I need to make a BalloonSat airframe for the flight computer and send it up.

However, I’m out of space this month. I hope what I’ve written so far will help some readers avoid making some of the mistakes I’ve made. Feel free to correct me and make suggestions. With any luck, I’ll have a really neat near space mission to write about this summer.

Onwards and Upwards, Your near space guide NV

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