[bootlin/training-materials updates] master: kernel: i2c-comm: Explain why the I2C bus needs pull-ups (205d7e38)
Thomas Petazzoni
thomas.petazzoni at bootlin.com
Fri Oct 29 10:46:40 CEST 2021
Repository : https://github.com/bootlin/training-materials
On branch : master
Link : https://github.com/bootlin/training-materials/commit/205d7e38865c5650cd2cf5728ceb30912ac0bef2
>---------------------------------------------------------------
commit 205d7e38865c5650cd2cf5728ceb30912ac0bef2
Author: Miquel Raynal <miquel.raynal at bootlin.com>
Date: Mon Jul 12 20:11:16 2021 +0200
kernel: i2c-comm: Explain why the I2C bus needs pull-ups
Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
>---------------------------------------------------------------
205d7e38865c5650cd2cf5728ceb30912ac0bef2
labs/kernel-i2c-communication/kernel-i2c-communication.tex | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/labs/kernel-i2c-communication/kernel-i2c-communication.tex b/labs/kernel-i2c-communication/kernel-i2c-communication.tex
index c4292164..4d5ee0e9 100644
--- a/labs/kernel-i2c-communication/kernel-i2c-communication.tex
+++ b/labs/kernel-i2c-communication/kernel-i2c-communication.tex
@@ -136,8 +136,11 @@ Here are details about the values:
\item \ksym{MUX_MODE2} corresponds to muxing mode 2, as explained in the
datasheet.
\item \ksym{PIN_INPUT_PULLUP} puts the pin in pull-up mode (remember
- that our pins support both pull-up and pull-down). It seems to
- be needed for I2C bus operation.
+ that our pins support both pull-up and pull-down). By design, an
+ I2C line is never actively driven high, devices either pull the
+ line low or let it floating. As we plug our device directly on the
+ bus without more analog electronics, we need to enable the
+ internal pull-up.
\end{itemize}
Now that pin muxing settings have been explained, edit your board
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