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https://github.com/juliannicholls/raspberry-pi-misc

Raspberry Pi programs of various types, including Rpi.gpio, gpiozero, pygame, C, PWM
https://github.com/juliannicholls/raspberry-pi-misc

gpio motor raspberry-pi

Last synced: 8 months ago
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Raspberry Pi programs of various types, including Rpi.gpio, gpiozero, pygame, C, PWM

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README 

          
# Raspberry Pi Miscellany



Files from my forays into programming for the [Raspberry Pi](http://raspberrypi.org).



Includes programs written in C, Python, Javascript, and a little Scratch.



Libraries used: RPi.GPIO, gpiozero, wiringPi, pygame, python-cwiid, and

soon Pygame Zero.



If anyone is interested enough in any of the below programs to read an

expanded blog article with diagrams and more code explanation, please 

contact me and I will write one.



----

## c



Use `make` to build the programs in here.



### pwm



Uses the PWM pin, physical pin 12 (GPIO18). The clock divisor, range, and duty

cycle value can all be set from a menu. It has been tried with an LED, a

speaker, and a 6V motor connected to the collector side of a PN2222 transistor.



I have also tried it with a servo, setting it up for 50Hz (20ms cycle time).

The duty cycle need s to be kept very low.



The frequencies quoted in the program have now been checked with a multimeter that

has a frequency function.



----

## python



General python programs.



### test_sleep



Test the resolution of `time.sleep()`.



It appears to be about 100us (microseconds), which is an order of magnitude 

(or more) better than I expected. time.sleep(n) ALWAYS sleeps for at least 

the time specified.



----

## python/gpio



A few programs to flash LEDs etc.



### flash18



Flashes an LED attached to Pin 12 (GPIO18).



### flash_12_26



Flashes two LEDs alternately, attached to pins 12 and 26 (GPIO18 & GPIO7).



### drive_speaker



Makes a 1kHz (ish) tone from a speaker attached to pin 12 (GPIO18).



### drive_lcd



A driver library for LCD displays attached to GPIO pins in a 4-bit configuration

The connections have been updated and the pin numbers changed to use BCM

numbering (see comments in the file for details).



When run directly, it starts by initializing the panel and writing 'SETUP'.

Then it waits for the user to hit enter between each of the next phases:

position the cursor to the beginning of the second line and write

'Second Line', then write 'End' at the end of the second line, after which

the cursor is shown, hidden, and set blinking before finally waiting for

the user to hit enter again and then disconnecting from GPIO.



### drive_lcd_20x4



An updated version of the drive_lcd program, specifically for a 20x4 display.

There is more cursor addressing in this one to reflect the extra lines.



### drive_12864



Drive a slightly strange 128x64 display. It seems that most either have an

I2C or SPI interface, or 8 data bits and 2 chip selects. The one I bought is

different, and has strange GDRAM addressing instead.



It turns out that mine would work on SPI too. it works perfectly connected to

an Arduino using the [U8glib library](https://github.com/olikraus/u8glib).



*See **python/st7920** below*



### lcd_clock



Displays a clock on the first line of a connected LCD display using the drive_lcd

library. See drive_lcd for the connection details. It ensures that it always

releases the GPIO pins by having a `try...except` round the main loop to trap Ctrl-C.



### delorean



Show the top line from the Delorean display, and the second line is the current

time.



### drive_7_segment



Drive a seven segment, common-anode, display. Connections can be seen inside

the file. Currently set up for B+, assuming a 40-pin GPIO.



First, it shows 0-F with a delay between each. Then, it shows 6 arrows pointing

forward and back, right and left. Finally, it shows each possible letter and waits

for the user to press enter.



The simplest way to change to a common-cathode display would be to swap the names

of `segment_on()` and `segment_off()`.



### traffic_lights



Simulate a (British) set of traffic lights with a Red, Amber, and Green LED

connected to pins 11, 13, and 15 respectively.



### motor



Turn a motor on and off connected to pin 12 via PN2222A transistor.



I wrote this so that I could turn the motor off quickly in case I'd made a bad

choice of transistor or another schoolboy error. The motor is connected to the

collector and powered by a wall-wart providing a range of voltages, I tried 6V

and 9V, but I initially tried it with the 5V line (pin 2) on the Pi GPIO and

that was fine too.



it turns out that my choice of transistor was OK. With pin 12 connected via a

4K Ohm resistor to the Base of the transistor, I'm drawing less than 1mA from

the Pi. The motor is drawing around 180mA when running freely. I'm going to try

stalling the motor a little to test its maximum draw once I have some crocodile

clips.



### read_ldr



Read a Light Dependent Resistor using the RC charge time of a capacitor. See

comments inside for details.



The circuit I used is a little different from the one suggested in the GPIO Zero

documents for [Light Sensor](https://gpiozero.readthedocs.org/en/v1.1.0/api_input.html#light-sensor-ldr)



### servo



Drive a servo connected to pin 25 using software PWM. I don't think it's very

practical, but that may be more to do with the low quality servo I'm using. The

software PCM is wavering between about 47Hz and 51Hz whereas the servo really

wants a steady 50Hz.



To drive a servo accurately needs the hardware PCM on GPIO18, I believe.



### clock / clock-ca



Drive a quad 7 segment display as a clock. `clock` drives a common-cathode display

and `clock-ca` drives a common-anode display. See this 

[Raspi.TV page](http://raspi.tv/2015/how-to-drive-a-7-segment-display-directly-on-raspberry-pi-in-python)

for wiring details.



----

## python/gpiozero



Examples using the GPIO Zero library.



### button_led



Using gpiozero library, switch a LED connected to GPIO17 on and off with a

button connected to GPIO21 and a GND.



### puffin



Emulate a complete British Puffin crossing. It has Red, Amber, and Green LEDs

for the cars, obviously. It uses a Red and Green LED for walk / don't walk

for pedestrians. It also uses another Red LED to indicate that the crossing

request button has been acknowledged.



### rgd_led



Drive a common-cathode RGB LED.



### robot2



Run a [CamJam Edukit 3 Robot](http://camjam.me/?page_id=1035).

Takes input from the user:



```

f        Forward for n steps

f   d       Forward until less than 10cm from obstacle

b        Backward for n steps

l        Left for n steps

r        Right for n steps

q           Quit

```



### fairy-lights



Control the battery-powered Christmas fairy lights that I bought this year. 

It randomly fades in and out and flashes at a couple of different speeds.



----

## python/pygame



Adventures in game / UI programming.



### bounce1



Bounce a (square!) ball around in a window.



### bounce2



Bounce a ball around in a box with a bouncy sound on each bounce. Use the cursor

keys to expand and contract the square that the ball is bouncing in.



----

## python/pygame/led_ui



Display buttons that turn LEDs on and off. Five buttons turn directly connected

LEDs on and off. Another seven buttons turn the segments of a display on and off.

Ten more buttons display the digits 0-9 on the 7-segment display and a final 25

buttons allow for most of the alphabet in upper or lower case.



See `main.py` and `.../gpio/drive_7_segment.py` for full connection details.



----

## python/wiimote



Examples using the python-cwiid library.

[The main CWiiD library information](https://help.ubuntu.com/community/CWiiD).



### wiimote



An example of using a Wiimote on a Pi, displays the state of the buttons and

the accelerometer data. It's a bit flaky with the £3.99 Wiimote clone that I

bought from eBay, It's a lot more stable with a genuine Nintendo one, the

rather noisy library can be squelched by using



```

    wiimote.py 2>/dev/null

```



if necessary.



### attitude



The beginning of a program to show the values returned from the accelerometers

with the Wiimote in different orientations. I have abandoned it for now

because my Wiimote clone is so flaky that there's no point continuing.



----

## python/st7920



Library for a 128x64 ST7920 panel connected via SPI based on

[Jamie Wood's ST7920 library](http://github.com/JMW95/pyST7920).



### test



Test the library by plotting a single pixel, drawing a rectangle, filled rectangle, 

and reverse filled rectangle, and outputting text which shows how long each redraw

takes (~114-118ms on my RPi2).



### show_ip



Show the IP address on the display. This could be used on a headless Pi to show its

address to allow logging in via SSH.



----

## python/robot



These are programs to drive a robot based on the [CamJam Edukit 3](http://camjam.me/?page_id=1035).



### 2-motors



Turn on both motors in one direction for 2 seconds.



### 3-driving



Move forward for a second, right for a second, and then left for a second.



### 4-line



Read the line-following sensor. Returns low (0V) for Black, and high (3.3V)

for white. It works at a distance of ~2.5cm (~1").



### 5-distance



Read the ultrasonic distance sensor. This returns high for the echo flight time.

This is then turned into a distance in cm.



A voltage divider is necessary to connect this to a Raspberry Pi because it is a 5V

peripheral. A 470R and a 330R resistor (provided in the EduKit 3) gives about 3V.



### 6-pwm



Use the software PWM in the `Rpi.GPIO` library to drive forward, right, and left at

about 30% power.



### raise_7890



Turn on all 4 lines. I was having trouble with the supplied H-bridge driver board,

so I needed to turn on all 4 lines that the board uses so that I could connect my

multimeter and see if there was voltage, which there wasn't with even one motor

connected.



**NB**: *This should not be run with motors connected.*



----

## python/atod-3202



Read a MCP3202 12-bit A/D over SPI.



----

## i2c



Use the Adafruit I2C library to drive a normal LED connected to the first pin,

an RGB LED connected to the second, third, and fourth pins on a MCP23017 chip,

changing its colour every time a button connected to the fifth I/O pin is pressed.



----

## node



A [Blynk library](http://www.blynk.cc) client program that updates Virtual Pin

9 with the seconds

from the current time, responds to a slider on V1, updating a graph attached

to V4, and has a terminal on V3 which feeds back and sends notifications.



----

## scratch



The beginnings of an alien game. N.B. I can't draw :-)