3 * Extend wiringPi with the MCP3004 SPI Analog to Digital convertor
4 * Copyright (c) 2012-2013 Gordon Henderson
5 ***********************************************************************
6 * This file is part of wiringPi:
7 * https://projects.drogon.net/raspberry-pi/wiringpi/
9 * wiringPi is free software: you can redistribute it and/or modify
10 * it under the terms of the GNU Lesser General Public License as
11 * published by the Free Software Foundation, either version 3 of the
12 * License, or (at your option) any later version.
14 * wiringPi is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with wiringPi.
21 * If not, see <http://www.gnu.org/licenses/>.
22 ***********************************************************************
26 #include <wiringPiSPI.h>
32 * Return the analog value of the given pin
33 *********************************************************************************
36 static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
38 unsigned char spiData [2] ;
39 unsigned char chanBits ;
40 int chan = pin - node->pinBase ;
42 chanBits = 0b11000000 | (chan << 3) ;
44 spiData [0] = chanBits ;
47 wiringPiSPIDataRW (node->fd, spiData, 2) ;
49 return ((spiData [0] << 7) | (spiData [1] >> 1)) & 0x3FF ;
55 * Create a new wiringPi device node for an mcp3004 on the Pi's
57 *********************************************************************************
60 int mcp3004Setup (const int pinBase, int spiChannel)
62 struct wiringPiNodeStruct *node ;
64 if (wiringPiSPISetup (spiChannel, 1000000) < 0)
67 node = wiringPiNewNode (pinBase, 8) ;
69 node->fd = spiChannel ;
70 node->analogRead = myAnalogRead ;