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POPython - How can I read input from a device using ioctl or spidev?
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copied!<p>I have a <a href="http://www.raspberrypi.org/phpBB3/viewtopic.php?t=56131&f=93" rel="nofollow">hardware device</a> and the vendor that supplied it gave a bit of C code to listen for button presses which uses <code>ioctl</code>. The device has an SSD1289 controller.</p> <blockquote> <p>Push buttons require no additional pins, their status canbe read over SPI.</p> </blockquote> <p>That's what I want, to read which push button was pressed.</p> <p>I am trying to replicate this script in Python for my own application, but the _IOR and ioctl requirements are throwing me off. </p> <pre><code>#include <stdio.h> #include <sys/types.h> #include <fcntl.h> #include <unistd.h> #include <string.h> #include <sys/ioctl.h> #define SSD1289_GET_KEYS _IOR('keys', 1, unsigned char *) void get_keys(int fd) { unsigned char keys; if (ioctl(fd, SSD1289_GET_KEYS, &keys) == -1) { perror("_apps ioctl get"); } else { printf("Keys : %2x\n", keys); } } int main(int argc, char *argv[]) { char *file_name = "/dev/fb1"; int fd; fd = open(file_name, O_RDWR); if (fd == -1) { perror("_apps open"); return 2; } while(1) get_keys(fd); printf("Ioctl Number: (int)%d (hex)%x\n", SSD1289_GET_KEYS, SSD1289_GET_KEYS); close (fd); return 0; } </code></pre> <p>Now I know that Python has an <a href="http://docs.python.org/2/library/fcntl.html" rel="nofollow">ioctl</a> module, and at some point I should be calling</p> <pre><code>file = open("/dev/fb1") buf = array.array('h', [0]) fcntl.ioctl(file, ????, buf, 1) </code></pre> <p>I can't figure out what the <code>SSD1289_GET_KEYS</code> is supposed to be. How do I get this and what is <code>_IOR</code>? </p> <p>Also, if this is the wrong approach, knowing that would be a help too. There are libraries such as <a href="http://tightdev.net/SpiDev_Doc.pdf" rel="nofollow">spidev</a> which are supposedly for SPI, but I don't know what to read using it. </p> <hr> <p>@alexis provided some useful steps below, which got me to this point:</p> <pre><code>import fcntl import array file = open("/dev/fb1") buf = array.array('h', [0]) fcntl.ioctl(file, -444763391, buf, 1) </code></pre> <p>Now, pressing a button changes the value of buf if I keep the above in a loop.</p>

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