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Re: Raspberry Pi I2C implementation still broken?
I can confirm the IOCTL is fixed, and can now successfully program I2C
EEPROMs using NetBSD on the Pi. Since my Pi is currently a wifi-less Model
A, I have no provisions to check out the source and try to fix the other
On a semi-related note: I've noticed that "Getting Started with GPIO"
documentation is limited compared to Linux. Probably a good idea would be
for someone (probably me, when I have time) to either port some Linux helper
libraries and/or write some documentation on how to use the I2C IOCTL.
While yes, reading the man pages and source code will get a potential hacker
the information required to succeed*, there are some who are new to (Net)BSD
and may just want to play around before delving into the details. It DOES
take a bit of time to get used to where to find good sources of info
(including the proper man page sections). Just a thought- probably would fit
well on the wiki.
Enclosed is a link to some sample code that programs Atmel EEPROMs using the
NetBSD IOCTL (in this case, AT24HC04B):
I have verified it to work, and hopefully after this example, those who want
to use more GPIO from the RPi can fill in the blanks. Of course, with
minimal tweaks, this code should work on ANY platform that NetBSD supports
that provides an I2C interface via GPIO :D.
*A FreeBSD GPIO/I2C RPi tutorial also exists, and is of course similar to
From: Jonathan A. Kollasch
Sent: Thursday, January 22, 2015 1:13 PM
To: William D. Jones
Subject: Re: Raspberry Pi I2C implementation still broken?
On Mon, Jan 05, 2015 at 11:31:54AM -0500, William D. Jones wrote:
According to the following bug report:
and mailing list posts:
Either the IOCTL or I2C driver the Raspberry Pi I2C implementation
is broken. I believe I may have found another bug in the
implementation by trying to read/write an I2C EEPROM using IOCTL,
but I'm guessing it is related to the already existing IOCTL issues
that cause writes to always succeed. It's also possible my sample
code is wrong :P. So, before I file a problem report: Has there been
any progress in fixing the above I2C write errors?
There has now;
(The ioctl was broken in certain situations.)
While port-arm/48855 and port-arm/48932 still remain, they should be easy
William D. Jones
Rowan University | ECE | 2012
Member Tau Beta Pi
Message sent using 'Windows Live Mail' client.
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