WiringPi comes with a separate program to help manage the GPIO. This program, called gpio, can also be used in scripts to manipulate the GPIO pins – set outputs and read inputs. It’s even possible to write entire programs just using the gpio command in a shell-script, although it’s not terribly efficient doing it that way Another way to call it is using the system function in C/C or it’s equivalent in other programming languages. The gpio command is designed to be installed as a setuid program and called by a normal user without using the sudo command (or logging in as root). In addition to using the gpio utility to control the GPIO pins, you can:. Export/Unexport pins via the /sys/class/gpio interface, where they will then be available to user programs (that then do not need to be run as root or with sudo).
Export pins to enable edge-triggered interrupts via the /sys/class/gpio interface. Control the pins on the PiFace peripheral device.
Load SPI and I2C modules and set /dev/ permissions to enable read/write by the user running the gpio program. Set the SPI buffer size and I2C baud rate (when loading the modules). Output values to the Gertboard DAC. Read inputs from the Gertboard ADC. Determine your Raspberry Pi board hardware revision. See the man page for the gpio program to see what all the features are by typing man gpio at the command prompt.
Usage From the Linux command line:. gpio -v This prints the version. gpio -g The optional -g flag causes pin numbers to be interpreted as BCMGPIO pin numbers rather than standard wiringPi pin numbers.
Standard input and output commands. gpio -g mode in/out/pwm/up/down/tri This sets the mode of a pin to be input, output or pwm and additionally can set the internal pull-up/down resistors to pull-up, pull-down or none.
gpio -g write 0/1 This sets an output pin to high (1) or low (0). gpio -g pwm Set the pin to a PWM value (0-1023 is supported). gpio -g read Reads and prints the logic value of the given pin. It will print 0 (low) or 1 (high). gpio readall This reads all the normally accessible pins and prints a table of their numbers (both wiringPi and BCMGPIO, so makes for a handy cross-reference chart), along with their modes and current values. Module Load Commands.
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gpio load spi buffer size in KB This loads the SPI kernel modules and optionally sets the internal buffer to the given size in KB (multiples of 1024). The default is 4KB and is usually more than enough for most application which only exchange a byte or 2 at a time over the SPI bus. The /dev/spi. entries are set to be owned by the person using the gpio program, so there is no need to run subsequent programs as root (unless they use other wiringPi functions). gpio load i2c baud rate in Kb/sec This loads the I2C kernel modules and optionally sets the baud rate to the given speed in Kb/sec (multiples of 1000).
The default is 100Kb/sec. The /dev/I2c.
entries are set to be owned by the person using the gpio program, so there is no need to run subsequent programs as root (unless they use other wiringPi functions) /sys/class/gpio mode commands. gpio export in/out This exports the given pin (BCM-GPIO pin number) as an input or output and makes it available for a user program running as the same user to use. gpio unexport Removes the export of the given pin. gpio unexportall Removes all /sys/class/gpio exports. gpio exports This prints a list of all gpio pins which have been exported via the /sys/class/gpio interface and their modes. gpio edge rising/falling/both/none This enables the given pin for edge interrupt triggering on the rising, falling or both edges. (Or none which disables it) Note: The pin numbers in the sys mode are always BCM-GPIO pin numbers.
Examples gpio mode 0 out gpio write 0 1 This uses the wiringPi pin numbers to set pin 0 as an output and then sets the pin to a logic 1. Gpio -g mode 0 in gpio -g read 0 This uses the BCMGPIO pin numbering scheme and reads pin 0 (SDA0 on a Rev.
1 Raspberry Pi) Internal pull up/down resistors The GPIO lines have internal pull up or pull-down resistors which can be controlled via software when a pin is in input mode. Gpio mode 0 up gpio mode 0 down gpio mode 0 tri These set the resistors to pull-up, pull-down and none respectively on wiringPi pin 0. PiFace Commands The PiFace is somewhat limited in that it has 8 inputs pins and 8 output pins and these are fixed in the hardware, so only the write and read commands are implemented:.
gpio -p write 0/1 Writes the value 0 (off) or 1 (on) to the output pin on the PiFace. gpio -p read Reads and prints the value on the given input pin. gpio -p mode up/tri This enables (up) or disables (tri) the internal pull-up resistor on the given input pin. You need to enable the pull-up if you want to read any of the on-board switches on the PiFace board. Thanks gordon, i have that LED blinking, added a printf(” LED blinking n”) so terminal showed a description. Is there a simple way to increment a number (0-255) and output it over pins (17 18 21 22 23 24 25 4) in binary.
Not looking for a full solution just a nudge. You can catch a single interrupt using wiringPi’s gpio command: gpio wfi 5 falling then it will wait for the falling edge of pin 5 – however the down-side is that it will stall your entire script waiting, but if that’s acceptible, then go for it, but if not, you’ll need to resort to polling the pins – you can use the gpio read command. Now If you’re a bash whiz, you could fire-off several bash functions using the & command and have each function wait on a different pin, when wait on one of the functions finishing, but it really starts to get messy – especaily in bash! With the application I’m considering the thing I need is accurate timestamps to go along with the interrupt notification – I seem to recall seeing somewhere an interface that grabbed a timestamp down in the kernel driver and passed it to userspace – does your interface do that or was I seeing that somewhere else? Thank you BTW for making this level of access possible – the project I’m doing will migrate at some point to a microcontroller but being able to do all the prototyping with Linux and the pi will be a big win.
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I’m not that familiar with the architecture of the ARM on the Pi to know if it has a TSC or not – however I do know that there must be something ticking over with microsecond accuracy as the gettimeofday system call returns it. There is also a spare timer which you can use which is 32-bits wide and counts up (or down) at 1MHz However then there is the issue of getting that time stamp back into userland along with the interrupt – and this is where it’s going to be a little sticky/tricky You’ll be delving into kernel/module land there, I fear So take the interrupt, call gettimeofday immediately and hope for the best -Gordon. It’s really the wrong device for this level of accuracy (IMO) However you might want to look at RISCOS rather than Linux as I understand it’s not a pre-emptive multitasking OS, so you may be a step closer to the hardware with a “lighter” OS to help you manage things.
The interrupt code was benchamrked (don’t have link to hand, sorry), but it did achieve about 20K interrupts/sec. That should be more than enough for 10ms timings.
It’s also possible to get sub 10uS timings too, but you need to poll the IO pin rather than wait for an interrupt, and even then, delays might be longer due to pre-emption in the kernel, but switching to real-time mode, and high priority will really help here. The down-side is that a busy loop in a high priority real-time process will more or less stall every other user-land program running -Gordon. Hi Gordon, Thanks for the fine website, code and tutorials. I just got my RPi today and have been tinkering around with it and having a lot of fun. I was hoping you could give me two minutes of advice My goal, and I’m not sure I have the skills, is to use the RPi to control an 1991 scrolling LED display I found for $5 at a yard sale. It has a proprietary EZKEY II keyboard that connects with a 14 pin cable.
My thought is I can replicate the required keystrokes using the GPIO outputs and WiringPi and/or Python. I’ve used a multimeter to capture the pin combinations that reflect the letters on the keyboard. However, I think it uses at least 10 of the pins and if I understand right the RPi can only control 8 pins for this. Beyond this, I’m not 100% sure what I’m up against yet but I’d appreciate any tips you might have.
Thank you very much for sharing this very powerful library and gpio tool with us. Since I am not an C programmer I stick to the gpio utility instead of the library and build everything I need around with custom shell scripts. That works well for me. I miss just one function in gpio. Maybee you can add it in one of the next versions (or as stand-alone tool): I want to run one (or more) daemons in the background which should trigger a handler script if a pin changes its value to a defined one (edge trigger). Of course I can do that with a polling script, but I am looking for an interrupt based solution to free as many resources of the RPi for other tasks.
I could imagine the following parameters for that function: – pin number – edge type (falling/raising/both) – handler script (eg myhandler.sh, $1=pin, $2=edgetype, $3=pinvalue) – quit when fired (OPTIONAL, default = yes) – timeout (OPTIONAL, max. Seconds to wait for a trigger before daemon quits, default = -1 / infinite) – command (set/check/kill): set new trigger, check if a trigger is set, kill trigger (assuming that only one trigger per pin can be defined) If I understood the library correct it should be able to build such a tool based on the wiringPiISR function. But, as said I am not a C programmer ? What do you think of such a trigger daemon extension of gpio? Best regards, Gregor.
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What if it were simply: gpio -g wfi timeout and at that point, it just waited for the interrupt then carried on? Then you could wait on any pin in a script and the script will simply carry on once the interrupt triggers – rather than have the gpio program call your script (which I think gets a bit messy) You would be able to wait on many different pins in differnet scripts if needed – and examin status to see if it timed out? That would be relatively easy to implent. How would it fit in your scenarios? Fast response ? that sounds even better.
Would that work that way? #define pins gpio mode 0 in gpio mode 0 up gpio edge 0 falling gpio mode 1 in gpio mode 1 up gpio edge 1 falling gpio mode 2 in gpio mode 2 up gpio edge 2 falling #wait for interrupt FIRED=`gpio wfi` #handle interrupt case $FIRED in 0 ) echo “pin 0”;; 1 ) echo “pin 1”;; 2 ) echo “pin 2”;; -1 ) echo “timeout”;;. ) echo “unkown”;; esac In this case two process would run in parallel.
The shell script waiting for gpio wfi and gpio itself. Would that be efficient, even if the RPi has to wait for days to get an event? (I really do not know). Background: I would like to use the RPi as interface for my alarm system. But in parallel other services like Asterisk shell run. That’s not quite the way I’d envidaged it, but maybe there’s something half way. Let me think about it.
Essentially GPIO is stateless between runs, so it doesn’t know what you did last time. So to watch multiple pins at the same time, then you’d (i’d) need to make it do that on the command-line. Gpio -g wfi 1:f 2:f 3:r maybe. Might just need a bit of command-line parsing Might also be the wrong tool for the job, but hey I do describe it as the swiss army knofe of gpio functions in the man page and it never ceases to amaze me what I see people doing with it!
As I said, there is no state rmemberd between GPIO executions, so 3 calls to gpio to set the directions, etc. Isn’t visible to the gpio command that waits for the interrupt – but I guess it could just wait for it and hope for the best. Really you should be writing stuff like this in C though – if someone had asid to me 10 years ago that a shell-script would be able to capture interrupts I’d have laughed but here we are doing just that ? But rather than run the gpio command in the background and have it call another progral (something I’m not keen to do at all), you could simply replace that with the suggestion I made earlier, so you’d write a separate script for each interrupt that went something like: #!/bin/sh while true; do gpio -g wfi 17 rising./dispatcher int17 done and so on. So you break your program down to several smaller scripts and you can then test each one individually too. And you can haev these as functions inside one big script and still execute the functions with & so it’s the function being backgrounded and the function that’s calling the script, not the gpio program. Part of the reason I don’t want gpio to call other scripts is that it runs as root (set uid), so I’d need to drop back to the uid of the calling user, then call the script – that’s not hard, but it’s one more thing to do and I do feel it’s getting away from what I wanted gpio to do – it really started off as nothing more than a test program for the wiringPi library, but like all good things, has mutated beyond it’s original use into a bit of a little monster, really ? -Gordon. First many thanks for this great product.
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I intend to use it to drive my Somfy sunshades from OpenRemote (see my post ) I use the following script: #!/bin/sh PIN=$1 gpio mode $PIN out gpio write $PIN 1 sleep 0.1 gpio write $PIN 0 This works fine if called from the Raspberry Pi command line. However if I call it from Javascript (Google V8 engine) with a system call, I do get error 32512. This error does not appear if I put a # sign before the last line. Anybody out here who has a clue of what may be wrong? Thanks, Pieter.
Raspberry Pi and the Serial Port By default the Raspberry Pi’s serial port is configured to be used for console input/output. Whilst this is useful if you want to login using the serial port, it means you can't use the Serial Port in your programs. To be able to use the serial port to connect and talk to other devices (e.g.
Arduino), the serial port console login needs to be disabled. Needless to say you will need some other way to login to the Raspberry Pi, and we suggest doing this over the network using an.
Disable Serial Port Login To enable the serial port for your own use you need to disable login on the port. There are two files that need to be edited The first and main one is /etc/inittab This file has the command to enable the login prompt and this needs to be disabled. Edit the file and move to the end of the file. You will see a line similar to T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100 Disable it by adding a # character to the beginning. Save the file. #T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100 Disable Bootup Info When the Raspberry Pi boots up, all the bootup information is sent to the serial port.
Disabling this bootup information is optional and you may want to leave this enabled as it is sometimes useful to see what is happening at bootup. If you have a device connected (i.e. Arduino) at bootup, it will receive this information over the serial port, so it is up to you to decide whether this is a problem or not. You can disable it by editing the file / boot / cmdline.
Txt The contents of the file look like this dwcotg.lpmenable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait Remove all references to ttyAMA0 (which is the name of the serial port). The file will now look like this dwcotg.lpmenable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait Reboot In order you enable the changes you have made, you will need to reboot the Raspberry Pi sudo shutdown -r now Test the Serial Port A great way to test out the serial port is to use the minicom program. If you dont have this installed run sudo apt-get install minicom Connect your PC to the Raspberry Pi serial port using an appropriate serial port adapter and wiring, then open Putty or a similar serial terminal program on PC side. Setup a connection using the serial port at 9600 baud. Now run up minicom on the Raspberry Pi using minicom -b 9600 -o -D /dev/ttyAMA0 What you type into the minicom terminal screen should appear on the serial PC terminal and vice versa.
Here’s how to add a 9-pin serial port to your Raspberry Pi, and it’ll only take you 10 mins. Well, maybe a couple of weeks to wait for the part to arrive from Hong Kong, but once it arrives, it’s only 10 minutes!
Dungeon siege ending. Just be sure to forward port 16000 for gameranger if you have any issues.
? Here’s the part you’ll need. It’s an RS232 to TTL converter module containing a MAX3232 chip. The MAX3232 is important, as the older MAX232 won’t handle the 3.3v levels of the Pi, whereas the Max3232 will. It comes with a 4-way cable for connecting the module to the GPIO of your Pi.
If you search on eBay for “RS232 Serial Port To TTL Converter Module MAX3232” you should find several. The one I got cost me €3 with free shipping from Hong Kong. Here’s another view, showing the bottom of the module, indicating the +5V, GND, Tx and Rx pins. Simply attach the cable to the module, and connect to the 5V, GND, UART Rx and UART Tx pins of the GPIO. And a closer view of the GPIO connections.
Wiringpi Digitalread
I removed the bolts from the module so that I could plug directly into the serial port of my laptop without a long serial cable. Once the module was attached to the laptop serial port, I downloaded PuTTY, and attached to the com port (usually COM1) at 115200 baud, 8 data bits, no parity, and no flow control. Once I applied the settings in PuTTY, I powered on the Raspberry Pi, and saw the entire boot process displayed out the UART of the Raspberry Pi and into PuTTY on the Laptop. A login prompt was displayed, and I could then log in over the UART as normal. Now to find a project that needs serial port access.
I do have a few in mind! Hi, we have one problem for about Rs232 example I want give or take 1 data Pi to PC, I can send to PC no problem but I cant take Pc to Pi any data if I send 30 times or 40 times after I can send PC to Pi then it be normaly but if I push caracter from keyboard after lock serial com after I send again 30 or 40 times data then open again after normaly I tried resister then I use max3232 but no change only I have problem for Pi to PC send wire example some example I have from internet “Pi serial com.
To ardiuno” but this not work I will wait your helps thanks a lot.
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