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--- chumbyhackerboard:i2c [2010/08/28 21:37]
ladyada created
+++ chumbyhackerboard:i2c [2016/01/28 18:05]
@@ Line 1: / Line 1: @@
-**THIS TUTORIAL IS STILL IN PROGRESS**
-====== i2c ======
-First, you'll need to have a toolchain installed so make sure you go back and install it!
-Next, scroll down and copy the i2c C code board. Open up your terminal to the CHB and type in **mkdir /mnt/storage/dev; cd /mnt/storage/dev; cat > i2c.c** into the terminal and hit return.
-Then paste in the code and finish by typing **Control-D**
-{{:chumbyhackerboard:i2ccopy.gif|}}
-Then compile the code with **gcc** by typing in **gcc -o i2c i2c.c** to create the **i2c** executable. Then run it and make sure you get the response below
-{{:chumbyhackerboard:i2ccompile.gif|}}
-====== Code ======
-<file>
-/*
- This software uses a BSD license.
-Copyright (c) 2010, Sean Cross / chumby industries
-All rights reserved.
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
- * Redistributions of source code must retain the above copyright
-   notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above copyright
-   notice, this list of conditions and the following disclaimer in the
-   documentation and/or other materials provided with the
-   distribution.
- * Neither the name of Sean Cross / chumby industries nor the names
-   of its contributors may be used to endorse or promote products
-   derived from this software without specific prior written
-   permission.
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- POSSIBILITY OF SUCH DAMAGE.
- */
-#include <stdio.h>
-#include <linux/i2c.h>
-#include <linux/i2c-dev.h>
-#include <fcntl.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <sys/ioctl.h>
-#include <string.h>
-#define I2C_FILE_NAME "/dev/i2c-0"
-#define USAGE_MESSAGE \
-    "Usage:\n" \
-    "  %s r [addr] [register]   " \
-        "to read value from [register]\n" \
-    "  %s w [addr] [register] [value]   " \
-        "to write a value [value] to register [register]\n" \
-    ""
-static int set_i2c_register(int file,
-                            unsigned char addr,
-                            unsigned char reg,
-                            unsigned char value) {
-    unsigned char outbuf[2];
-    struct i2c_rdwr_ioctl_data packets;
-    struct i2c_msg messages[1];
-    messages[0].addr  = addr;
-    messages[0].flags = 0;
-    messages[0].len   = sizeof(outbuf);
-    messages[0].buf   = outbuf;
-    /* The first byte indicates which register we'll write */
-    outbuf[0] = reg;
-    /*
-     * The second byte indicates the value to write.  Note that for many
-     * devices, we can write multiple, sequential registers at once by
-     * simply making outbuf bigger.
-     */
-    outbuf[1] = value;
-    /* Transfer the i2c packets to the kernel and verify it worked */
-    packets.msgs  = messages;
-    packets.nmsgs = 1;
-    if(ioctl(file, I2C_RDWR, &packets) < 0) {
-        perror("Unable to send data");
-        return 1;
-    }
-    return 0;
-}
-static int get_i2c_register(int file,
-                            unsigned char addr,
-                            unsigned char reg,
-                            unsigned char *val) {
-    unsigned char inbuf, outbuf;
-    struct i2c_rdwr_ioctl_data packets;
-    struct i2c_msg messages[2];
-    /*
-     * In order to read a register, we first do a "dummy write" by writing
-     * 0 bytes to the register we want to read from.  This is similar to
-     * the packet in set_i2c_register, except it's 1 byte rather than 2.
-     */
-    outbuf = reg;
-    messages[0].addr  = addr;
-    messages[0].flags = 0;
-    messages[0].len   = sizeof(outbuf);
-    messages[0].buf   = &outbuf;
-    /* The data will get returned in this structure */
-    messages[1].addr  = addr;
-    messages[1].flags = I2C_M_RD/* | I2C_M_NOSTART*/;
-    messages[1].len   = sizeof(inbuf);
-    messages[1].buf   = &inbuf;
-    /* Send the request to the kernel and get the result back */
-    packets.msgs      = messages;
-    packets.nmsgs     = 2;
-    if(ioctl(file, I2C_RDWR, &packets) < 0) {
-        perror("Unable to send data");
-        return 1;
-    }
-    *val = inbuf;
-    return 0;
-}
-int main(int argc, char **argv) {
-    int i2c_file;
-    // Open a connection to the I2C userspace control file.
-    if ((i2c_file = open(I2C_FILE_NAME, O_RDWR)) < 0) {
-        perror("Unable to open i2c control file");
-        exit(1);
-    }
-    if(argc > 3 && !strcmp(argv[1], "r")) {
-        int addr = strtol(argv[2], NULL, 0);
-        int reg = strtol(argv[3], NULL, 0);
-        unsigned char value;
-        if(get_i2c_register(i2c_file, addr, reg, &value)) {
-            printf("Unable to get register!\n");
-        }
-        else {
-            printf("Register %d: %d (%x)\n", reg, (int)value, (int)value);
-        }
-    }
-    else if(argc > 4 && !strcmp(argv[1], "w")) {
-        int addr = strtol(argv[2], NULL, 0);
-        int reg = strtol(argv[3], NULL, 0);
-        int value = strtol(argv[4], NULL, 0);
-        if(set_i2c_register(i2c_file, addr, reg, value)) {
-            printf("Unable to get register!\n");
-        }
-        else {
-            printf("Set register %x: %d (%x)\n", reg, value, value);
-        }
-    }
-    else {
-        fprintf(stderr, USAGE_MESSAGE, argv[0], argv[0]);
-    }
-    close(i2c_file);
-    return 0;
-}
-</file>

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