├── README
├── mcp23017.py
└── mcp23017.wsgi


/README:
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 1 | Python MCP230XX I2C IO Expander Tools
 2 | -------------------------------------
 3 | 
 4 | A couple of basic tools I knocked up while playing with the MCP23017 on my Raspberry Pi. More info on my blog here: http://nathan.chantrell.net
 5 | 
 6 | 
 7 | mcp23017.py
 8 | -----------
 9 | A simple command line tool for setting outputs as high or low.
10 | 
11 | Usage: mcp23017.py -b <bank> -o <output> -s <high|low>
12 | 
13 | eg. to set GPA1 high: mcp23017.py -b a -o 1 -s high
14 | 
15 | Response: Output GPA1 changed to high
16 | 
17 | Requires python-smbus
18 | 
19 | 
20 | mcp23017.wsgi
21 | -------------
22 | 
23 | A web interface using Python and modwsgi. Can be controlled through the built in web form or via GET requests with optional JSON like responses. 
24 | 
25 | eg. to set output GPA1 high: 
26 | http://rpi/mcp23017.wsgi?bank=a&output=1&state=high&mode=json
27 | 
28 | Response: {"GPA1":"HIGH"}
29 | 
30 | Requires python-smbus and apache with mod-wsgi. Note that you will need to make sure your web server has permissions for the i2c bus, eg. /dev/i2c-0
31 | 
32 | To do: Extend to cater for input as well as output and report on the current state of the outputs.
33 | 


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/mcp23017.py:
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 1 | #! /usr/bin/python
 2 | 
 3 | # A simple Python command line tool to control an MCP23017 I2C IO Expander
 4 | # By Nathan Chantrell http://nathan.chantrell.net
 5 | # GNU GPL V3 
 6 | 
 7 | import smbus
 8 | import sys
 9 | import getopt
10 |  
11 | bus = smbus.SMBus(0) # For revision 1 Raspberry Pi, change to bus = smbus.SMBus(1) for revision 2.
12 | 
13 | address = 0x20 # I2C address of MCP23017
14 | bus.write_byte_data(0x20,0x00,0x00) # Set all of bank A to outputs 
15 | bus.write_byte_data(0x20,0x01,0x00) # Set all of bank B to outputs 
16 | 
17 | 
18 | # Let them know how it works
19 | def usage():
20 |    print 'Usage: mcp23017.py -b <bank> -o <output> -s <high|low>'
21 | 
22 | # Handle the command line arguments
23 | def main():
24 |    try:
25 |       opts, args = getopt.getopt(sys.argv[1:],"hb:o:s:",["bank=","output=","state="])
26 | 
27 |       if not opts:
28 |         usage()
29 |         sys.exit(2)
30 | 
31 |    except getopt.GetoptError:
32 |       usage()
33 |       sys.exit(2)
34 | 
35 |    for opt, arg in opts:
36 |       if opt == '-h':
37 |          usage()
38 |          sys.exit()
39 |       elif opt in ("-b", "--bank"):
40 |          bank = arg
41 |       elif opt in ("-o", "--output"):
42 |          output = int(arg)
43 |       elif opt in ("-s", "--state"):
44 |          state = arg
45 | 
46 | # Set the correct register for the banks
47 |    if bank == "a" :
48 |     register = 0x12
49 |    elif bank == "b" :
50 |     register = 0x13
51 |    else:
52 |     print "Error! Bank must be a or b"
53 |     sys.exit()
54 | 
55 | # Read current values from the IO Expander
56 |    value =  bus.read_byte_data(address,register) 
57 | 
58 | # Shift the bits for the register value, checking if they are already set first
59 |    if state == "high":
60 |     if (value >> output) & 1 :
61 |      print "Output GP"+bank.upper()+str(output), "is already high."
62 |      sys.exit()
63 |     else:
64 |       value += (1 << output)
65 |    elif state == "low":
66 |     if (value >> output) & 1 :
67 |      value -= (1 << output)
68 |     else:
69 |      print "Output GP"+bank.upper()+str(output), "is already low."
70 |      sys.exit()
71 |    elif state == "read":
72 |     if (value >> output) & 1 :
73 |      print "high"
74 |     else:
75 |      print "low"
76 |     sys.exit()
77 |    else:
78 |     print "Error! state must be high or low"
79 |     sys.exit()
80 | 
81 | # Now write to the IO expander
82 |    bus.write_byte_data(address,register,value)
83 |  
84 | # Tell them what we did
85 |    print "Output GP"+bank.upper()+str(output), "changed to", state
86 | 
87 | if __name__ == "__main__":
88 |    main()
89 | 


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/mcp23017.wsgi:
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  1 | #!/usr/bin/python
  2 | 
  3 | # A basic Python and modwsgi interface to the MCP23017 I2C IO Expander
  4 | # Built in web form or use GET requests, add &mode=json for JSON like responses
  5 | # By Nathan Chantrell http://nathan.chantrell.net
  6 | # GNU GPL V3
  7 | 
  8 | from wsgiref.simple_server import make_server
  9 | from cgi import parse_qs, escape
 10 | import smbus
 11 | import sys
 12 | import getopt
 13 | 
 14 | bus = smbus.SMBus(0) # For revision 1 Raspberry Pi, change to bus = smbus.SMBus(1) for revision 2.
 15 | 
 16 | address = 0x20 # I2C address of IO Expander
 17 | bus.write_byte_data(0x20,0x00,0x00) # Set all of bank A to outputs 
 18 | bus.write_byte_data(0x20,0x01,0x00) # Set all of bank B to outputs 
 19 | 
 20 | # The HTML used to build the full web page option
 21 | html = """
 22 | <html>
 23 | <body>
 24 |    <form method="get" action="mcp23017.wsgi">
 25 |       <p>
 26 |          <b>Bank</b><br />
 27 |          <input name="bank" type="radio" value="a"> A 
 28 |          <input name="bank" type="radio" value="b"> B <br />
 29 |          </p>
 30 |       <p>
 31 |          <b>Output</b><br />
 32 |          <input name="output" type="radio" value="0"> 0 <br />
 33 |          <input name="output" type="radio" value="1"> 1 <br />
 34 |          <input name="output" type="radio" value="2"> 2 <br />
 35 |          <input name="output" type="radio" value="3"> 3 <br />
 36 |          <input name="output" type="radio" value="4"> 4 <br />
 37 |          <input name="output" type="radio" value="5"> 5 <br />
 38 |          <input name="output" type="radio" value="6"> 6 <br />
 39 |          <input name="output" type="radio" value="7"> 7 <br />
 40 |          </p>
 41 |       <p>
 42 |          <b>state:</b>
 43 |          <input name="state" type="radio" value="high"> High
 44 |          <input name="state" type="radio" value="low"> Low
 45 |          </p>
 46 |       <p>
 47 |          <input type="submit" value="Submit">
 48 |          </p>
 49 |       </form>
 50 |    <p>
 51 |       Bank: %s<br>
 52 |       Output: %s<br>
 53 |       State: %s<br>
 54 |       Debug: %s
 55 |       </p>
 56 |    </body>
 57 | </html>
 58 | """
 59 | 
 60 | # HTML for the minimal JSON response (activated with &mode=json in the query string)
 61 | htmlshort = """{"%s%s":"%s"}"""
 62 | 
 63 | def application(environ, start_response):
 64 | 
 65 |    # Get the query string variables
 66 |    d = parse_qs(environ['QUERY_STRING'])
 67 |    bank = d.get('bank', [''])[0] 
 68 |    output = d.get('output', ['8'])[0] 
 69 |    state = d.get('state', [''])[0] 
 70 |    mode = d.get('mode', [''])[0]
 71 | 
 72 |    # Escape user input
 73 |    bank = escape(bank)
 74 |    output = int(escape(output))
 75 |    state = escape(state)
 76 |    mode = escape(mode)
 77 | 
 78 |    # Set the correct register for the banks
 79 |    if bank == "a" :
 80 |     register = 0x12
 81 |    elif bank == "b" :
 82 |     register = 0x13
 83 |    else:
 84 |     register = 0
 85 | 
 86 |    # Read current values from the IO Expander
 87 |    value =  bus.read_byte_data(address,register)
 88 | 
 89 |    # Shift the bits for the register value, checking if they are already set first
 90 |    if state == "high":
 91 |     if not (value >> output) & 1 :
 92 |      value += (1 << output)
 93 |    elif state == "low":
 94 |     if (value >> output) & 1 :
 95 |      value -= (1 << output)
 96 |    else:
 97 |      state = "none"
 98 | 
 99 |    # Quick sanity check
100 |    if (0 <= output < 8) and register != 0 and state != "none":
101 |     # Looks OK, now write to the IO expander
102 |     bus.write_byte_data(address,register,value)
103 |     if mode == "json" : # minimal mode
104 |      response_body = htmlshort % (bank.upper(), output, state.upper())
105 |     else: # otherwise show full web page
106 |      response_body = html % (bank.upper(), output, state.upper(), value)
107 |    elif mode == "json" :
108 |     response_body = "SYNTAX ERROR"
109 |    else:
110 |     response_body = html % ("n/a", "n/a", "n/a", value)
111 | 
112 |    # Show the HTML page
113 |    status = '200 OK'
114 |    response_headers = [('Content-Type', 'text/html'),
115 |                        ('Content-Length', str(len(response_body)))]
116 |    start_response(status, response_headers)
117 |    return [response_body]
118 | 
119 | 


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