GPIO Interrupt

[sheershak-agarwal]

Hi I want to integrate gps pps into my system and i want the exact time when my pps goes high through the gpio. I saw the setting GPIO_INT. How do I use it?

[timcanham]

What GPIO_INT are you referring to?

[sheershak-agarwal]

fprime/Drv/LinuxGpioDriver/LinuxGpioDriverComponentImpl.hpp

Line 54 in 0845912

GPIO_INT //!< interrupt

[timcanham]

Ah - if you configure it as GPIO_INT, it will configure the GPIO to invoke the intOut port. The port contains an argument with the latched time of the interrupt. For Linux, it is system time.

[sheershak-agarwal]

Okay, so it won't really help me get pps time. How do you recommend getting pps signal?

[timcanham]

If you tie the GPS PPS to a GPIO, then the time in the port call would be the system time of the pulse. If the pulse is a "time at the tone," you could use that to correlate system time to GPS time.

[sheershak-agarwal]

by port call do you mean when I read the gpio? How can we make sure that we are reading the gpio when it is high?

[timcanham]

It looks like the interrupt is hard-coded for a rising edge:

fprime/Drv/LinuxGpioDriver/LinuxGpioDriverComponentImpl.cpp

Line 333 in 0845912

stat = gpio_set_edge(compPtr->m_gpio, "rising");

So if you set the direction as GPIO_INT, the driver will call the intOut output port whenever the driver sees the GPIO go high. You don't have to call anything, but you have to start the task waiting on the interrupt:

fprime/Drv/LinuxGpioDriver/LinuxGpioDriverComponentImpl.hpp

Line 48 in 0845912

Os::Task::TaskStatus startIntTask(NATIVE_INT_TYPE priority, NATIVE_INT_TYPE cpuAffinity = -1);

You would add a Svc::Cycle port to your component that wants to receive the interrupt and connect it to that port on the GPIO driver. The GPIO driver is modal; you can poll it for a change or you can configure it to interrupt on change.

[sheershak-agarwal]

Thank you. I will try that tomorrow and ask more question if stuck

[sheershak-agarwal]

Ok so what I am doing is:

1. Add the Svc::Cycle port in my Gps module
2. Connect the Svc::Cycle input port with the GPIO Port in the AppTopologyAi.xml
3. Generate new cpp and hpp file and then use the cycle in function for timing correction.

[sheershak-agarwal]

Hello, so I am doing the sets below and facing an error.

1. Add PpsRead Port in my Gps Component.
   <port name="PpsRead" data_type="Svc::Cycle" kind="async_input" max_number="1"> <comment> Output Port for reading GPIO values </comment> </port>
2. Create new Impl.cpp and hpp files
3. Open the gpio26Driver (assigned to pps) as GPIO_INT in Topology.cpp
   if (not gpio26Drv.open(26,Drv::LinuxGpioDriverComponentImpl::GPIO_INT)) { Fw::Logger::logMsg("[ERROR] Failed to open PS GPIO 26\n"); } else { Fw::Logger::logMsg("[INFO] Opened PS GPIO 26\n"); }
4. Connected the ppsRead port to the gpioDriver
   <connection name = "gpio26"> <source component = "gps" port = "PpsRead" type = "Svc::Cycle" num = "0"/> <target component = "gpio26Drv" port = "inOut" type = "Svc::Cycle" num = "0"/> </connection>

During the fprime-util install, I got this error:
/home/sheershak/Desktop/F-Prime-Debug/App/build-fprime-automatic-raspberrypi/App/Top/AppTopologyAppAc.cpp:292:9: error: ‘class App::GpsComponentImpl’ has no member named ‘set_PpsRead_OutputPort’; did you mean ‘get_PpsRead_InputPort’? gps.set_PpsRead_OutputPort(0, gpio26Drv.get_inOut_InputPort(0)); ^~~~~~~~~~~~~~~~~~~~~~ get_PpsRead_InputPort /home/sheershak/Desktop/F-Prime-Debug/App/build-fprime-automatic-raspberrypi/App/Top/AppTopologyAppAc.cpp:292:45: error: ‘class Drv::LinuxGpioDriverComponentImpl’ has no member named ‘get_inOut_InputPort’; did you mean ‘set_intOut_OutputPort’? App/Top/CMakeFiles/App.dir/build.make:148: recipe for target 'App/Top/CMakeFiles/App.dir/AppTopologyAppAc.cpp.obj' failed gps.set_PpsRead_OutputPort(0, gpio26Drv.get_inOut_InputPort(0)); ^~~~~~~~~~~~~~~~~~~ set_intOut_OutputPort make[2]: *** [App/Top/CMakeFiles/App.dir/AppTopologyAppAc.cpp.obj] Error 1 CMakeFiles/Makefile2:6473: recipe for target 'App/Top/CMakeFiles/App.dir/all' failed make[1]: *** [App/Top/CMakeFiles/App.dir/all] Error 2 Makefile:135: recipe for target 'all' failed make: *** [all] Error 2 [ERROR] CMake erred with return code 2

[sheershak-agarwal]

So the question here is, in my gps component, should the kind be async_input or output? and where do I start the task waiting on the interrupt?

[timcanham]

The GPIO from the GPS receiver is driving your component, so the GPIO driver should be the source. Your GPS component would be async_input or sync_input. async_input would dispatch a message, while sync_input would invoke your handler directly, so you may have to guard your data against multiple threads.

[timcanham]

As for a task, you could make your GPS component active, so it would have it's own thread to service the interrupt, since it is called by the GPIO driver.

[sheershak-agarwal]

The GPS Component is active. Oh ok I will make the gpioDriver as source and the cycle as target. Thanks