GPIO

All posts tagged GPIO

Mio for Raspberry Pi

Posted by epsilon on May 17, 2013
Posted in: Code, RPi-Arduino. Tagged: , , , , , , . Leave a comment

mio.py is “my” io library for Raspberry Pi. At present it is a kind of “hello world” program that demonstrates how work with one digital input, e.g., a switch, and one digital output, e.g., an LED. Below are (a) a photo of the Raspberry rigged up with a circuit managed by miO, (b) a description of the package, (c) some output on the command line, (d) a circuit diagram.

The (Python) code is at github.

(a) MIO RUNNING ON PI

mio-pi-2

(b) MIO: COMMAND SUMMARY

Suppose that LED is pin 17 and SWITCH is pin 23:

  • blink(LED, 0.1, 0.3) — blink LED, on for 0.1 second, off for 0.3 seconds
  • read(SWTICH) — read SWITCH: print 1 ON the first time it is closed, then the time it was held closed when it opens, then print 2 ON when it is closed the second time, etc.
  • control(LED, SWITCH) — control LED with SWITCH. This function is like read, except that the LED blinks when the switch is closed.

These functions can be invoked fromt the command line: (a) sudo python mio.py blink, (b) sudo python mio.py read, (c) sudo python mio.py control.

(c) SOME OUTPUT

pi@raspberrypi ~/gpio $ sudo python3 mio.py read
    1 ON
      1.09
    2 ON
      1.75
    3 ON
      0.13
    4 ON
      0.11

(d) CIRCUIT DIAGRAM

Let the switch have terminals A and B.

   A --- 3.3V

              |--- 1K resistor --- Pin 23
   B --- T ---|
              |--- 10K resistor ---GND

   Pin 17 --- LED --- 330 Ohm resistor --- GND

PiFace – the basics

Posted by epsilon on May 12, 2013
Posted in: Code, RPi-Arduino. Tagged: , , , , , , . 1 Comment

PiFace is an IO board for the Raspberry Pi computer — 8 buffered inputs, 8 outputs, and two relays that theoretically can handle 10 amperes at 230 volts. See Gordon’s Projects for a full review. The model allows you to disconnect the relays from two of the outputs, and there is a Python interface. To test the board (and my understanding of it), I rigged up a simple circuit with one external switch — a Morse code type key — one, LED, and one resistor. Below are photos of (i) the PiFace board riding on top of the Raspberry Pi, (ii) the circuit board (iii) the whole kit-and-kaboodle, (iv) the circuit.

The code for running the circuit is at gitHub. (i) Use on(7) and off(7) to turn the LED on an off manually; 7 is the pin the LED is wired to; (ii) use blink(7) for a more exciting test; (iii) use read(0) to read the switch, which is attached to pin 0; (iv) use control(7,0) to control LED on pin 7 by the switch on pin 0 — flip the switch attached to pin 0 and ground to turn on the LED on pin 7. Of course all this is ridiculous overkill, but the idea is to get started and to test the PiFace + Raspberry Pi combo.

Note added: Stephen Visser has an excellent article on the PiFace.

PiFace

PiFace sitting on top of Raspberry Pi

Breadboard circuit

Breadboard circuit

Kit and Kaboodle

Kit and Kaboodle

Schematic

Schematic