It's fairly trivial. On the driver side you want to use a wait queue that gets
woken up in response to an interrupt from the ioport, you will have to look up
what sort of interrupts are available for that port.
Here's a sketch:
in the ISR:
/* Interrupt has occured */
rc=waitqueue_active(&wait_q);
if (rc) {
atomic_set(&irq_occured,1);
wake_up_interruptible(&wait_q);
}
in the POLLING function:
_poll(struct file *filp, poll_table *wait) {
int mask = 0;
/* Did irq occur? */
if (atomic_read(&irq_occured)) {
mask = POLLIN | POLLRDNORM;
atomic_set(&irq_occured,0);
} else {
/* otherwise we go to sleep */
poll_wait(filp, &wait_q, wait);
}
/* Returning a 0 will cause the select()/poll() to block */
return mask;
}
On Wednesday, June 11, 2014 12:40:37 PM, "Jonathan Leslie
[ts-7000]" <> wrote:
OK, that sounds great! how do I do that? Any examples around?
>________________________________
> From: " [ts-7000]" <>
>To: "" <>
>Sent: Wednesday, June 11, 2014 12:34 PM
>Subject: Re: [ts-7000] wanted: a C/BASH coded example of a program woken up by
>an input momentary switch.
>
>
>
>
>You need write a driver that services the dio port interrupt. Then your user
>program sleeps on the driver via the polling mechanism i.e. by select() and is
>woken up when a interrupt occurs.
>
>
>Mike McDonald
>On Wednesday, June 11, 2014 12:03:31 PM, " [ts-7000]"
><> wrote:
>
>
>
>
>OK, so I have DIO.C working perfectly (code below) and I have a Momentary
>switch hooked up to DIO_40, and an LED hooked up to DIO_33 and everything
>works perfectly. I can turn on and off the LED, with a "./dio set "
>command, and when I look at pin 40 with the "./dio get 40" command it properly
>answers with a 0 or 1 depending on the state of the push button.
>
>
>What I want is a program that is interrupt based that uses little to no CPU
>time but wakes up when the DIO_40 changes states, I know I can put the
>"getdiopin(pin);" statement in a while loop and have it break out when the
>state changes, but that burns a lot of CPU time, or if "sleep" is utilized,
>then there will be a delay to respond.
>
>
>Is there any way to make a [threaded?] program where you have [a child thread
>that is just] waiting for the change of state of pin 40, not looping, and
>checking, When I write ethernet drivers, I have a multithreaded process
>where a child thread is waiting on an inbound message and it just sits there
>doing nothing, buring no CPU, until it gets woken up by traffic on the IP
>port. I want something similar for an input button. Any Ideas?
>
>
>
>
>/*******************************************************************************
>* Program:
>* Get DIO (dio.c)
>* Technologic Systems TS-7500 with TS-752 Development Board
>*
>* Summary:
>* This program will accept any pin number between 5 and 40 and attempt to get
>* or set those pins in a c program rather than scripted. You will need the
>* TS-7500 and TS-752 development board. Although this program will enable the
>* use of said pins, it will primarily enable the use of the 8 Inputs, 3
>Outputs,
>* and Relays on the TS-752. Keep in mind that if a GND or PWR pin is read (or
>* something else unlogical, we don't necessarily care about the output because
>* it could be simply "junk".
>* Notice careful semaphore usage (sbuslock, sbusunlock) within main.
>*
>* Usage:
>* ./dio <get|set> <pin#> <set_value (0|1|2)>
>*
>* 0 - GND
>* 1 - 3.3V
>* 2 - Z (High Impedance)
>*
>* Examples:
>* To read an input pin (such as 1 through 8 on the TS-752):
>* ts7500:~/sbus# ./dio get 40
>* Result of getdiopin(38) is: 1
>*
>* To set an output pin (such as 1 through 3 or relays on the TS-752):
>* ts7500:~/sbus# ./dio set 33 0
>* Pin#33 has been set to 0 [You may verify with DVM]
>*
>* Compile with:
>* gcc -mcpu=arm9 dio.c sbus.c -o dio
>
>
>
>
>Date Whom Notes.
>100112 JL Lets give it a try.
>
>
>
>
>
>
>*******************************************************************************/
>#include "sbus.h"
>#include <assert.h>
>#include <string.h>
>#include <stdio.h>
>
>
>#define DIO_Z 2
>
>
>/*******************************************************************************
>* Main: accept input from the command line and act accordingly.
>*******************************************************************************/
>int main(int argc, char **argv)
>{
> int pin;
> int val;
> int returnedValue;
>
>
> // Check for invalid command line arguments
> if ((argc > 4) | (argc < 3))
> {
> printf("Usage: %s <get|set> <pin#> <set_value (0|1|2)>\n", argv[0]);
> return 1;
> }
>
>
> // We only want to get val if there are more than 3 command line arguments
> if (argc == 3)
> pin = strtoul(argv[2], NULL, 0);
> else
> {
> pin = strtoul(argv[2], NULL, 0);
> val = strtoul(argv[3], NULL, 0);
> }
>
>
> // If anything other than pins 5 through 40, fail program
> assert(pin <= 40 && pin >= 5);
>
>
> // Parse through the command line arguments, check for valid inputs, and
>exec
> if (!(strcmp(argv[1], "get")) && (argc == 3))
> {
> sbuslock();
> returnedValue = getdiopin(pin);
> sbusunlock();
>
>
> printf("pin#%d = %d \n", pin, returnedValue);
> }
> else if(!(strcmp(argv[1], "set")) && (argc == 4) && (val <= 2))
> {
> sbuslock();
> setdiopin(pin, val);
> sbusunlock();
>
>
> printf("pin#%d set to %d\n", pin, val);
> }
> else
> {
> printf("Usage: %s <get|set> <pin#> <set_value (0|1|2)>\n", argv[0]);
> return 1;
> }
> return 0;
>}
>// EOF
>
>
>
>
>
>
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