On Mon, 15 Jun 2020 15:08:18 -0700 (PDT), in
gmane.comp.hardware.beagleboard.user P B
<mmmbarley-re5jqeeqqe8avxtiumw...@public.gmane.org> wrote:
>Unfortunately, I also want
>P9-12 (GPIO 60) as pulldown output to turn on pump 1 using a relay, where
>P9-12's default state is pullup input, and
>P9-15 (GPIO 48) as pulldown output to turn on pump 2 using a relay, where
>P9-15's default state is pulldown input.
>
>I have been trying to work through RCN's dtb-rebuilder with Derek Molloy's
>book to accomplish this.
First or second edition? It may be pertinent.
>
>But I have not impacted this default state.
>
OTOH, I note you mentioned checking using config-pin, but not trying to
set using it. Have you tried using config-pin at run time instead of all
this DTB hassle? {the /old/ config-pin script, not the less-capable binary
that is now in the path}
-=-=-=-
debian@beaglebone:~$ config-pin -h
GPIO Pin Configurator
Usage: config-pin -c <filename>
config-pin -l <pin>
config-pin -q <pin>
config-pin <pin> <mode>
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -h
config-pin [-a] <pin> <mode>
Set <pin> to <mode>, configuring pin multiplexing and optionally
configuring the gpio. Valid <mode> strings vary based on <pin>,
however all pins have a default and gpio mode. The default mode is
the reset state of the pin, with the pin mux set to gpio, the pull
up/down resistor set to it's reset value, and the pin receive buffer
enabled. To setup gpio, the following <mode> strings are all valid:
gpio :
Set pinmux to gpio, existing direction and value unchanged
in | input:
Set pinmux to gpio and set gpio direction to input
out | output :
Set pinmux to gpio and set gpio direction to output
hi | high | 1 :
Set pinmux to gpio and set gpio direction to output driving
high
lo | low | 0 :
Set pinmux to gpio and set gpio direction to output driving low
To enable pull-up or pull-down resistors, a suffex may be appended to
any of the above gpio modes. Use + or _pu to enable the pull-up
resistor
and - or _pd to enable the pull-down resistor. Examples:
in+ | in_pu:
Enable pull-up resistor and setup pin as per input, above.
hi- | hi_pd:
Enable pull-down resistor and setup pin as per high, above.
While the pull-down resistor will be enabled, it will not do
much
until application software changes the pin direction to input.
config-pin -l <pin>
list valid <mode> values for <pin>
config-pin -i <pin>
show information to <pin>
config-pin -q <pin>
query pin and report configuration details
config-pin -f [file]
Read list of pin configurations from file, one per line
Comments and white-space are allowed
With no file, or when file is -, read standard input.
config-pin -h
Display this help text
debian@beaglebone:~$
-=-=-=- <snipping irrelevant>
debian@beaglebone:~$ /opt/scripts/device/bone/show-pins.pl
P9.15 16 R13 fast rx down 7 gpio 1.16
ocp/P9_15_pinmux (pinmux_P9_15_default_pin)
P9.12 30 U18 fast rx up 7 gpio 1.28
ocp/P9_12_pinmux (pinmux_P9_12_default_pin)
debian@beaglebone:~$ config-pin -q p9.12
Current mode for P9_12 is: default
debian@beaglebone:~$ config-pin -q p9.15
Current mode for P9_15 is: default
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -q
p9.12
P9_12 Mode: default Direction: in Value: 1
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -q
p9.15
P9_15 Mode: default Direction: in Value: 1
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin p9.12
out_pd
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin p9.15
out_pd
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -q
p9.12
P9_12 Mode: gpio_pd Direction: out Value: 0
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -q
p9.15
P9_15 Mode: gpio_pd Direction: out Value: 0
debian@beaglebone:~$ config-pin -q p9.12
Current mode for P9_12 is: gpio_pd
debian@beaglebone:~$ config-pin -q p9.15
Current mode for P9_15 is: gpio_pd
debian@beaglebone:~$
-=-=-=-
{the "modern" config-pin binary seems to lack an ability to set direction,
but does have gpio_pd/gpio_pu; the old script version has direction and
option to set _pu/_pd on the direction: out, out_pu, out_pd, in, in_pu,
in_pd}
As an aside -- setting an output to pull-up/pull-down seems to me
rather perverse. My understanding of circuits is that pull-up/-down is
meant to ensure one reads a particular state when external devices are
/not/ driving a line to either rail, or are tri-stated (floating) when the
line is shared among devices. Once your application is running, your
outputs should be driven to one or the other state, they won't be floating.
>From the script config-pin help:
"""
While the pull-down resistor will be enabled, it will not do
much
until application software changes the pin direction to input.
"""
{config-pin, either version, are not available if using the BB AI -- that
board must use device tree edits}
--
Dennis L Bieber
--
For more options, visit http://beagleboard.org/discuss
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