[FE training-materials-updates] kernel i2c communication lab: pin muxing paragraph

Michael Opdenacker michael.opdenacker at free-electrons.com
Mon Sep 30 09:39:32 CEST 2013

Repository : git://git.free-electrons.com/training-materials.git

On branch  : kernel-ng
Link       : http://git.free-electrons.com/training-materials/commit/?id=6fc821ea9756ec3d809c7d5e07122f03ed8bd085


commit 6fc821ea9756ec3d809c7d5e07122f03ed8bd085
Author: Michael Opdenacker <michael.opdenacker at free-electrons.com>
Date:   Mon Sep 30 09:38:33 2013 +0200

    kernel i2c communication lab: pin muxing paragraph
    Signed-off-by: Michael Opdenacker <michael.opdenacker at free-electrons.com>


 .../kernel-i2c-communication.tex                   |   30 +++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/labs/kernel-i2c-communication/kernel-i2c-communication.tex b/labs/kernel-i2c-communication/kernel-i2c-communication.tex
index 495f731..c181243 100644
--- a/labs/kernel-i2c-communication/kernel-i2c-communication.tex
+++ b/labs/kernel-i2c-communication/kernel-i2c-communication.tex
@@ -1,5 +1,5 @@
 \subchapter{Using the I2C bus}{Objective: make the I2C bus work and
-use it to implement communication with the Nunchuck device}
+use it to implement communication with the Nunchuk device}
 After this lab, you will be able to:
@@ -8,3 +8,31 @@ After this lab, you will be able to:
 \item Access I2C device registers through the bus
+Stay in the \code{~/felabs/linux/src/linux} directory for kernel and DTB
+compiling (stay in the \code{nunchuk} branch), and in
+\code{~/felabs/linux/modules/nfsroot/nunchuk} for module compiling
+(use two different terminals).
+\section{Add pinctrl properties to the Device Tree}
+As you found in the previous lab, we now managed to have our nunchuk
+device enumerated on the \code{i2c1} bus.
+However, to access the bus data and clock signals, we need to configure
+the pin muxing of the SoC.
+If you go back to the BeagleBone Black System Reference Manual, in the
+{\em Connector P9} section, you can see that the pins \code{17} and
+\code{18} that we are using correspond to pins \code{A16} and \code{B16}
+of the AM335 SoC. You can also see that such pins need to be configured 
+as \code{MODE2} to get the functionality that we need (\code{I2C1_SCL}
+and \code{I2C1_SDA}).
+Now look at the Device Tree for the AM335x EVM board
+(\code{arch/arm/boot/dts/am335x-evm.dts}). It's using \code{i2c1} too.
+Edit the \code{arch/arm/boot/dts/am335x-bone-common.dtsi} file and 
+add what's needed to enable pin muxing for \code{i2c1}.
+Don't hesitate to go back to the lectures to understand what to do!

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