Halloween candy vending machine
Software
The preconfigured Python image from the PiXtend website [6] lets you start programming as quickly as possible. Make sure the image matches the PiXtend model you use. To do so, search for the PiXtend Python Library heading on the page for the respective device.
Once you have downloaded the image and written it to an SD card, the PiXtend Python Library (PPL) is available directly. You only need to install the library to control the WS2812 LEDs. These steps are summarized in the first eight lines of Listing 1. To test whether the library installation was successful, run the strandtest.py program (lines 9 and 10).
Listing 1
Installing PPL
01 $ cd ~ 02 $ sudo apt update 03 $ sudo apt upgrade 04 $ sudo apt install build-essential python-dev python-pip unzip wget scons swig 05 $ wget https://github.com/jgarff/rpi_ws281x/archive/master.zip unzip master.zip 06 $ cd rpi_ws281x-master 07 $ sudo scons 08 $ sudo pip install rpi_ws281x 09 $ cd ~/rpi_ws281x-master/python 10 $ sudo PYTHONPATH=".:build/lib.linux-armv7l-2.7" python examples/strandtest.py
In the source code, you can configure different settings for the LEDs, including the LED_BRIGHTNESS parameter for the brightness of the diodes. You will want to choose a value that is as low as possible, because the LEDs consume a lot of current at full light intensity, and they also heat up.
Control
The ws.py program (Listing 2) [7] controls the eyes and mouth. At the start of the program you will find the TRANSLATE table that enables linear access to the individual LEDs. As mentioned earlier, the way the LEDs are installed on the panels is a little strange.
Listing 2
ws.py
01 import time
02 from neopixel import *
03 import argparse
04
05 LED_COUNT = 384
06 LED_PIN = 12
07 LED_FREQ_HZ = 800000
08 LED_DMA = 10
09 LED_BRIGHTNESS = 16
10 LED_INVERT = False
11 LED_CHANNEL = 0
12
13 TRANSLATE = [0, 15, 16, 31, 32, 47, 48, 63, 64, 79, 80, 95, 96, 111, 112, 127, 128, 143, 144, 159, 160, 175, 176, 191, 192, 207, 208, 223, 224, 239, 240, 255, 256, 271, 272, 287, 288, 303, 304, 319, 320, 335, 336, 351, 352, 367, 368, 383, 1, 14, 17, 30, 33, 46, 49, 62, 65, 78, 81, 94, 97, 110, 113, 126, 129, 142, 145, 158, 161, 174, 177, 190, 193, 206, 209, 222, 225, 238, 241, 254, 257, 270, 273, 286, 289, 302, 305, 318, 321, 334, 337, 350, 353, 366, 369, 382, 2, 13, 18, 29, 34, 45, 50, 61, 66, 77, 82, 93, 98, 109, 114, 125, 130, 141, 146, 157, 162, 173, 178, 189, 194, 205, 210, 221, 226, 237, 242, 253, 258, 269, 274, 285, 290, 301, 306, 317, 322, 333, 338, 349, 354, 365, 370, 381, 3, 12, 19, 28, 35, 44, 51, 60, 67, 76, 83, 92, 99, 108, 115, 124, 131, 140, 147, 156, 163, 172, 179, 188, 195, 204, 211, 220, 227, 236, 243, 252, 259, 268, 275, 284, 291, 300, 307, 316, 323, 332, 339, 348, 355, 364, 371, 380, 4, 11, 20, 27, 36, 43, 52, 59, 68, 75, 84, 91, 100, 107, 116, 123, 132, 139, 148, 155, 164, 171, 180, 187, 196, 203, 212, 219, 228, 235, 244, 251, 260, 267, 276, 283, 292, 299, 308, 315, 324, 331, 340, 347, 356, 363, 372, 379, 5, 10, 21, 26, 37, 42, 53, 58, 69, 74, 85, 90, 101, 106, 117, 122, 133, 138, 149, 154, 165, 170, 181, 186, 197, 202, 213, 218, 229, 234, 245, 250, 261, 266, 277, 282, 293, 298, 309, 314, 325, 330, 341, 346, 357, 362, 373, 378, 6, 9, 22, 25, 38, 41, 54, 57, 70, 73, 86, 89, 102, 105, 118, 121, 134, 137, 150, 153, 166, 169, 182, 185, 198, 201, 214, 217, 230, 233, 246, 249, 262, 265, 278, 281, 294, 297, 310, 313, 326, 329, 342, 345, 358, 361, 374, 377, 7, 8, 23, 24, 39, 40, 55, 56, 71, 72, 87, 88, 103, 104, 119, 120, 135, 136, 151, 152, 167, 168, 183, 184, 199, 200, 215, 216, 231, 232, 247, 248, 263, 264, 279, 280, 295, 296, 311, 312, 327, 328, 343, 344, 359, 360, 375, 376]
14
15 strip = Adafruit_NeoPixel(LED_COUNT, LED_PIN, LED_FREQ_HZ, LED_DMA, LED_INVERT, LED_BRIGHTNESS, LED_CHANNEL)
16 strip.begin()
17
18 f = open("data.bin","rt")
19 data=f.readlines()
20 bitcounter=0
21 image=2
22 for line in data:
23 if len(line)<3:
24 bitcounter=0
25 image=image+1
26 strip.show()
27 time.sleep(0.1)
28 if not(line.find("#")):
29 continue
30 bits = line.split(" ")
31 for bit in bits:
32 bit=bit.strip()
33 if len(bit) > 0:
34 if bit=='1':
35 strip.setPixelColor(TRANSLATE[bitcounter], Color(0,255,0))
36 else:
37 strip.setPixelColor(TRANSLATE[bitcounter], Color(0,0,0))
38 bitcounter=bitcounter+1
39 f.close
The information as to which LED is switched is provided in the data.bin file; Listing 3 shows an excerpt. Bit patterns control the LEDs. You can store any number of patterns for ws.py to send to the LEDs in sequence. It parses the file line-by-line and converts the data to commands for the LEDs. An empty line initiates a new bit pattern; the program skips comment lines that start with a hash symbol (#).
Listing 3
data.bin (Excerpt)
# 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 # 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0
Program
The control program (Listing 4) continuously queries the PiXtend's inputs and starts the conveyor belts alternately when the light barrier is triggered. In parallel to starting the belts, it calls two additional programs: One controls the LEDs, and the other plays back the matching creepy sound. If the play command doesn't work as intended, you can try connecting and configuring an external sound card to the Rasp Pi. Figure 4 shows the eyes and mouth. To see the whole setup working, check out my YouTube video [8].
Listing 4
halloween.py
01 #!/usr/bin/env python
02 # coding=utf-8
03
04 from __future__ import print_function
05 # Import Pixtend class
06 from pixtendlib import Pixtend
07 import time
08 import sys
09 import threading
10 import os, platform
11
12 p = Pixtend()
13
14 # Open SPI bus for communication
15 try:
16 p.open()
17 except IOError as io_err:
18 # Print error text and delete PiXtend instance
19 print("Error opening the SPI bus! Error is: ", io_err)
20 p.close()
21 p = None
22
23 def thread_sound():
24 os.system("play gost.wav")
25
26 def thread_animation():
27 os.system("sudo python ws.py")
28
29 # -----------------------------------------------------
30 # Main Program
31 # -----------------------------------------------------
32 if p is not None:
33 print("Running Main Program - Hit Ctrl + C to exit")
34 # Set some variables needed in the main loop
35 is_config = False
36 switch = True
37 pressed = False
38 while True:
39 try:
40 # Using Auto Mode for optimal SPI bus usage
41 if p.auto_mode() == 0:
42 if not is_config:
43 is_config = True
44 # Space for setup
45 print (p.digital_input0,":",p.digital_input1)
46 if p.digital_input2 == p.ON and pressed==False:
47 pressed=True;
48 x = threading.Thread(target=thread_sound)
49 x.start()
50 y = threading.Thread(target=thread_animation)
51 y.start()
52 if switch: p.digital_output0 = p.ON
53 else : p.digital_output1 = p.ON
54 switch=not(switch)
55 if p.digital_output0 == p.ON and di0_old == 0 and p.digital_input0 == p.ON:
56 p.digital_output0 = p.OFF
57 pressed=False
58 if p.digital_output1 == p.ON and di1_old == 0 and p.digital_input1 == p.ON:
59 p.digital_output1 = p.OFF
60 pressed=False
61 di0_old = p.digital_input0
62 di1_old = p.digital_input1
63 else:
64 print("Auto Mode - Communication is not yet up...Please wait...")
65 # Wait at minimum 0.1sec or 100ms before getting new values
66 time.sleep(0.1)
67 except KeyboardInterrupt:
68 # Keyboard interrupt caught, Ctrl + C, now clean up and leave program
69 p.close()
70 p = None
71 break
72 else:
73 # If there was an error when opening the SPI bus interface, leave the program.
74 print("")
75 print("There was a problem with the PiXtend communication. Quitting.")
76 print("")
Figure 4: The vending machine's eyes and mouth.
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