On Mon, 10 May 2021 13:33:01 -0700, in gmane.comp.hardware.beagleboard.user
"John Dammeyer" <[email protected]> wrote:
>To deal with CAN bus on the Pi3/Pi4 requires access to the SPI bus for the
>MCP2515. On the Beagle it's the on chip CAN device. And if I want to talk to
>sensors like I2C or One-Wire plus inexpensive LCD displays I need access to
>the hardware.
>
>So I installed the PXL library and that's where I ran into the next roadblock.
> First you can't, from within the IDE and debugging, work with SPI bus without
>running Lazarus as root. Or it just won't work with the /sys/class/gpio
>folders. And that's the reason for wanting to free up access to the gpio.
>
>The SPI bus ADAfruit application for a 320x240 display written in Python runs
>properly rendering LENNA.JPG onto the LCD display. The key outputs are the DC
>and RESET which are on gpio48 and gpio60. An "ls" of the /sys/class/gpio
>folder shows on start up those two are not visible.
>
SPI and I2C rely upon a different PINMUX configuration than GPIO...
GPIO is pretty much all "mode 7". SPI0 pins are "mode 0" and SPI1 pins are
"mode 3".
http://www.ofitselfso.com/BeagleNotes/BeagleboneBlackPinMuxModes.php
>It's possible to use:
>$ sudo echo 48 > /sys/class/gpio/export
Really?
debian@beaglebone:~$ sudo echo 48 > /sys/class/gpio/export
[sudo] password for debian:
echo: write error: Operation not permitted
To my knowledge, the redirection part is still done as the debian user,
only the echo is being done by sudo.
debian@beaglebone:~$ sudo su
root@beaglebone:/home/debian# echo 48 > /sys/class/gpio/export
>to create the gpio48 folder and as super user the VXP library can do that but
>then it fails on the write to SPI.
>
SPI0 appears on P9_17, _18, _21, and _22 (raw GPIO # 5, 4, 3, 2, aka
gpio0_5, ...). SPI1 are on P9_28, _29, _30, _31 (raw GPIO # 113, 111, 112,
110, aka gpio3_17, _15, _16, _14).
GPIO # 48 (gpio1_16) on P9_15 has no modes for SPI.
debian@beaglebone:~$ ls -l /sys/bus/spi/devices
total 0
lrwxrwxrwx 1 root root 0 Dec 31 1999 spi0.0 ->
../../../devices/platform/ocp/48030000.spi/spi_master/spi0/spi0.0
lrwxrwxrwx 1 root root 0 Dec 31 1999 spi0.1 ->
../../../devices/platform/ocp/48030000.spi/spi_master/spi0/spi0.1
lrwxrwxrwx 1 root root 0 Dec 31 1999 spi1.0 ->
../../../devices/platform/ocp/481a0000.spi/spi_master/spi1/spi1.0
lrwxrwxrwx 1 root root 0 Dec 31 1999 spi1.1 ->
../../../devices/platform/ocp/481a0000.spi/spi_master/spi1/spi1.1
debian@beaglebone:~$
debian@beaglebone:~$ ls -l /sys/devices/platform/ocp/48030000.spi/
total 0
lrwxrwxrwx 1 root gpio 0 May 10 15:42 driver ->
../../../../bus/platform/drivers/omap2_mcspi
-rw-rw-r-- 1 root gpio 4096 May 10 15:42 driver_override
-r--r--r-- 1 root gpio 4096 May 10 15:42 modalias
lrwxrwxrwx 1 root gpio 0 May 10 15:42 of_node ->
../../../../firmware/devicetree/base/ocp/spi@48030000
drwxrwxr-x 2 root gpio 0 May 10 15:42 power
drwxrwxr-x 3 root gpio 0 May 10 15:42 spi_master
lrwxrwxrwx 1 root gpio 0 May 10 15:42 subsystem ->
../../../../bus/platform
-rw-rw-r-- 1 root gpio 4096 May 10 15:42 uevent
debian@beaglebone:~$
debian@beaglebone:~$ ls -l
/sys/devices/platform/ocp/48030000.spi/spi_master/spi0
total 0
lrwxrwxrwx 1 root gpio 0 May 10 15:42 device -> ../../../48030000.spi
lrwxrwxrwx 1 root gpio 0 May 10 15:42 of_node ->
../../../../../../firmware/devicetree/base/ocp/spi@48030000
drwxrwxr-x 2 root gpio 0 May 10 15:42 power
drwxrwxr-x 5 root gpio 0 May 10 15:42 spi0.0
drwxrwxr-x 5 root gpio 0 May 10 15:42 spi0.1
drwxrwxr-x 2 root gpio 0 May 10 15:42 statistics
lrwxrwxrwx 1 root gpio 0 May 10 15:42 subsystem ->
../../../../../../class/spi_master
-rw-rw-r-- 1 root gpio 4096 May 10 15:42 uevent
debian@beaglebone:~$
NOTE: there are two config-pin in Buster, maybe even Stretch. The one
you get if you just enter "config-pin" is a compiled executable with some
limitations (if there is no pinmux file found it objects). I'm using the
older PERL script version which has a few more capabilities.
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -i
p9_15
Pin name: P9_15
Function if no cape loaded: gpio
Function if cape loaded: default gpio gpio_pu gpio_pd gpio_input pwm
Function information: gpio1_16 default gpio1_16 gpio1_16 gpio1_16 gpio1_16
ehrpwm1_tripzone_input
Kernel GPIO id: 48
PRU GPIO id: 80
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -i
p9_17
Pin name: P9_17
Function if no cape loaded: gpio
Function if cape loaded: default gpio gpio_pu gpio_pd gpio_input spi_cs i2c
pwm pru_uart
Function information: gpio0_5 default gpio0_5 gpio0_5 gpio0_5 gpio0_5
spi0_cs0 i2c1_scl ehrpwm0_synci pru_uart
Kernel GPIO id: 5
PRU GPIO id: 37
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 -q
p9_17
P9_17 Mode: default Direction: in Value: 1
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -l
p9_15
default gpio gpio_pu gpio_pd gpio_input pwm
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -l
p9_17
default gpio gpio_pu gpio_pd gpio_input spi_cs i2c pwm pru_uart
debian@beaglebone:~$
>=============================================================================
>debian@ebb:~/lazarus/pxl/Samples/FreePascal/SingleBoard/Generic/DisplaySPI$
>sudo ./DisplaySPI
>[sudo] password for debian:
>An unhandled exception occurred at $00032BB0:
> ESysfsSPITransfer: Cannot
> transfer <1> data byte(s) through SPI bus.
> $00032BB0 TSYSFSSPI__TRANSFER, line 247
> of /home/debian/lazarus/pxl/Source/PXL.Sysfs.SPI.pas
> $00032AC4
> TSYSFSSPI__WRITE, line 228 of
> /home/debian/lazarus/pxl/Source/PXL.Sysfs.SPI.pas
>=============================================================================
>
Since you haven't shown the code, I don't know what pins that call is
attempting to access. Especially as you earlier mention gpio 48 -- which
from what I can tell does not have SPI features. For the others, you may
need to pin-mux to activate SPI -- the default may be for them to be GPIO..
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin p9_17
spi_cs
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin p9_18
spi
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin p9_22
spi_sclk
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -q
p9_18
P9_18 Mode: spi
debian@beaglebone:~$
Using the other SPI device is trickier -- I believe a device tree
overlay needs to be specified in /boot/uEnv.txt. Config-pin fails
debian@beaglebone:~$
/opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin p9_31
spi_sclk
P9_31 pinmux file not found!
bash: /sys/devices/platform/ocp/ocp*P9_31_pinmux/state: No such file or
directory
Cannot write pinmux file: /sys/devices/platform/ocp/ocp*P9_31_pinmux/state
debian@beaglebone:~$ ls /opt/source/bb.org-overlays/src/arm/BB*SPI*
/opt/source/bb.org-overlays/src/arm/BBBLUE-GP0-SPI-00A0.dts
/opt/source/bb.org-overlays/src/arm/BB-LCD-ADAFRUIT-18-SPI1-00A0.dts
/opt/source/bb.org-overlays/src/arm/BB-SPI0-ADS8688-0A00.dts
/opt/source/bb.org-overlays/src/arm/BB-SPI0-AT86RF233-00A0.dts
/opt/source/bb.org-overlays/src/arm/BB-SPI0-MCP23S08-00A0.dts
/opt/source/bb.org-overlays/src/arm/BB-SPI0-MCP3008-00A0.dts
/opt/source/bb.org-overlays/src/arm/BB-SPIDEV0-00A0.dts
/opt/source/bb.org-overlays/src/arm/BB-SPIDEV1-00A0.dts
--
Dennis L Bieber
--
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