Hardware Reference
In-Depth Information
1-Wire Driver
The default GPIO pin used for the 1-Wire driver is GPIO 4. This is hard-coded in the
following kernel source file:
arch/arm/mach-bcm2708/bcm2708.c
If you need to change this default, alter the line in bcm2708.c that defines the macro
W1_GPIO:
#define W1_GPIO 4
Then rebuild your kernel.
Header P5
Be careful with the orientation of this Model B Rev 2.0 header strip. See Figure 3-2 : while
looking down at P1, with its pin 1 at the lower left, the P5 strip has its pin 1 at the upper
left (note the square pad on either side of the PCB).
Figure 3-2. P5's pin 1 location on the Rev 2.0 Model B
As a practical matter, I found that the pins for P5 can be soldered into the PCB with
some care (they are not included). However, the proximity of P5 to P1 makes it impossible
to plug in a header connector to P1 and P5 at the same time. With the pins installed, it
is possible to use individual wire plugs on the pins as needed. I ended up plugging in a
dual-wire plug on P5-04 and P5-06, which is one row away from P1. These wires were
then brought out to connectors on a wood strip for easier access.
By default, GPIO pins 28 through 31 are configured for driving 16 mA. (Chapter 10
has more information about this.)
 
Search WWH ::




Custom Search