I tried to use write operation on /sys/class/gpio/gpio14 (gpio15)/value,
but nothing happens (from
https://github.com/RobertPHeller/JAVALinuxGPIO/blob/main/LinuxGPIO.java )
I figured out that PrintStream doesn't throw exceptions so I tried to use
FileOutputStream.
Then I got exception:
java.io.IOException: Operation not permitted
at java.io.FileOutputStream.write(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:290)
Read operation via FileInputStream is ok.
I run my java application with "sudo".
gpio14 ... P9_24 (UART1_TXD)
gpio15 ... P9_26 (UART1_RXD)
Right?
Dátum: utorok 29. júna 2021, čas: 16:42:45 UTC+2, odosielateľ: Dennis Bieber
> On Tue, 29 Jun 2021 07:02:06 -0700 (PDT), in
> gmane.comp.hardware.beagleboard.user Radovan Chovan
> <[email protected]> wrote:
>
> >Thanks for all your comments.
> >
> >Is there any mapping between /sys/class/gpio and schematic diagram of
> >Beaglebone Black board?
> >
> Does
> https://vadl.github.io/beagleboneblack/2016/07/29/setting-up-bbb-gpio
> provide any help.
>
> >I want to use pin P9_24 (UART1_TXD) and P9_26 (UART1_RXD).
> >https://beagleboard.org/static/beaglebone/BEAGLEBONE_SCHEM_A3.pdf (page
> >11/11)
> >
> P9_24 equates to GPIO15, but in raw pin numbering appears to be 97. As
> I recall, there are 32 GPIOs per "CHIP", so that might be the 4th CHIP
> (counting from 0), and the second GPIO (again, counting from 0)
>
> >>> divmod(97, 32)
> (3, 1)
>
> P9_26 -> GPIO14, raw 96...
>
> >>> divmod(96, 32)
> (3, 0)
> >>>
>
> HOWEVER,
> debian@beaglebone:~$ gpioinfo
> gpiochip0 - 32 lines:
> line 0: "MDIO_DATA" unused input active-high
> <SNIP>
> line 12: "UART1_CTSN" "P9_20" input active-high [used]
> line 13: "UART1_RTSN" "P9_19" input active-high [used]
> line 14: "UART1_RXD" "P9_26" input active-high [used]
> line 15: "UART1_TXD" "P9_24" input active-high [used]
> line 16: "GMII1_TXD3" unused input active-high
>
> indicates that it is CHIP0, and the "line" 14/15 map to the GPIOxx (so for,
> say, GPIO45 it becomes chip 1, line 13)
>
> The gpioinfo command is provided by installing the gpiod package.
>
>
> debian@beaglebone:~$
> /opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -i
> p9_26
> Pin name: P9_26
> Function if no cape loaded: gpio
> Function if cape loaded: default gpio gpio_pu gpio_pd gpio_input uart can
> i2c pru_uart pruin
> Function information: gpio0_14 default gpio0_14 gpio0_14 gpio0_14 gpio0_14
> uart1_rxd dcan1_tx i2c1_sda pru_uart pru1_in16
> Kernel GPIO id: 14
> PRU GPIO id: 46
> debian@beaglebone:~$
> /opt/source/bb.org-overlays/tools/beaglebone-universal-io/config-pin -i
> p9_24
> Pin name: P9_24
> Function if no cape loaded: gpio
> Function if cape loaded: default gpio gpio_pu gpio_pd gpio_input uart can
> i2c pru_uart pruin
> Function information: gpio0_15 default gpio0_15 gpio0_15 gpio0_15 gpio0_15
> uart1_txd dcan1_rx i2c1_scl pru_uart pru0_in16
> Kernel GPIO id: 15
> PRU GPIO id: 47
> debian@beaglebone:~$
>
>
> (Unfortunately, that script doesn't tell one what "default" mode IS for the
> pin, but does have more capability than the compiled config-pin that
> replaces it)
>
>
> --
> Dennis L Bieber
>
>
--
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