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POwrite() returns -1 when writing to I2C_SLAVE device
primarykey
Id
16625301
data
AcceptedAnswerId
16629179
AnswerCount
2
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-05-18T14:21:09.797
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0
LastActivityDate
2013-05-19T19:54:47.403
LastEditDate
2013-05-18T14:43:27.677
LastEditorUserId
1747088
OwnerUserId
1747088
ParentId
0
PostTypeId
1
Score
1
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1714
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text
Body
I've read through the <a href="http://www.mjmwired.net/kernel/Documentation/i2c/dev-interface" rel="nofollow">Linux kernel documents on i2c</a> and written a code to try to replicate the command <code>i2cset -y 0 0x60 0x05 0xff</code> The code that I've written is here: <pre><code>#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 <stdint.h> #include <string.h> int main(){ int file; file = open("/dev/i2c-0", O_RDWR); if (file < 0) { exit(1); } int addr = 0x60; if(ioctl(file, I2C_SLAVE, addr) < 0){ exit(1); } __u8 reg = 0x05; __u8 res; __u8 data = 0xff; int written = write(file, &reg, 1); printf("write returned %d\n", written); written = write(file, &data, 1); printf("write returned %d\n", written); } </code></pre> When I compile and run this code I get: write returned -1 write returned -1 I've tried to follow exactly what the docs tell me, my understanding is that the address is set first with the call to <code>ioctl</code>, then I need to <code>write()</code> the register and then the data that I want sent to the register. I've also tried to use use SMbus, but I can't get my code to compile using this, it complains at the linking stage that it can't find the functions. Have I made any mistakes in this code? I'm a beginner to <code>i2c</code> and don't have a lot of experience with <code>c</code> either. EDIT: errno give the following message: <code>Operation not supported</code>. I am logged in as root on this machine though, so I don't think it can be a permissions thing, although I may be wrong.
Tags
<c><linux><i2c>
Title
write() returns -1 when writing to I2C_SLAVE device
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PostAcceptedAnswerId
1. PO
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 PTAnswer
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1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USJames
UserOwnerUserId
1. USJames
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1. This table or related slice is empty.
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1. PO
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 PTAnswer
2. PO
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