GPIO Access
In the previous chapter, we created a component for temperature monitoring. In this component, the corresponding outputs are set depending on the CPU temperature.
In the rest of this chapter, I would like to explain how the temperature monitoring status is forwarded to the GPIO ports of the Raspberry Pi.
Gpio Pin Access
The SignalF controller contains a hardware-independent abstraction of the GPIO ports. So that we can use this, we first create a new signal provider definition and a signal provider configuration. To do this, we add the following extension method:
private static ISignalFConfiguration AddGpioPinAccess(this ISignalFConfiguration configuration)
{
configuration.AddGpioPinAccessDefinition<IGpioPinAccess>(builder =>
{
builder.SetName("GpioPinAccessDefinition")
.UseTemplate("DefaultTemplate")
.AddSignalSinkDefinition("OK")
.AddSignalSinkDefinition("Warning")
.AddSignalSinkDefinition("Alarm")
.AddSignalSinkDefinition("Fan");
});
configuration.AddGpioPinAccessConfiguration(builder =>
{
builder.SetName("GpioPinAccess")
.UseDefinition("GpioPinAccessDefinition")
.AddSignalSinkConfiguration("OK", "OK")
.AddSignalSinkConfiguration("Warning", "Warning")
.AddSignalSinkConfiguration("Alarm", "Alarm")
.AddSignalSinkConfiguration("Fan", "Fan")
.AddSignalToChannelMapping("OK", "GPIO.GPIO17")
.AddSignalToChannelMapping("Warning", "GPIO.GPIO22")
.AddSignalToChannelMapping("Alarm", "GPIO.GPIO27")
.AddSignalToChannelMapping("Fan", "GPIO.GPIO18");
});
return configuration;
}
As mentioned above, Gpio Pin Access is hardware-independent. However, so that we can control the hardware pins, we need a new method in addition to the methods used so far for configuring signal sources and sinks: AddSignalToChannelMapping.
This allows the virtual pins in Gpio Pin Access to be assigned to the real hardware pins.
In the Hardware Access block, we see the Device Bindings component. This component is responsible for establishing communication with the hardware (e.g. sensors) or with other measurement systems. The Signal Flow block contains the device-specific implementations such as Gpio or sensors such as the BME280. Communication between the device bindings and the device implementations takes place via protocol-specific but hardware-independent channels, which are combined in channel groups.
Device binding
SignalF already contains a set of device bindings for the .NET IoT Libraries. This also includes the binding for Gpio, which we are using here.
The integration is quite simple. All we have to do is call the AddGpioDeviceBinding method in the SignalF configuration and specify a name for the binding.
private static ISignalFConfiguration AddGpio(this ISignalFConfiguration configuration)
{
return configuration.AddGpioDeviceBinding(builder => { builder.SetName("GPIOController"); })
.AddGpioChannelGroup()
.AddGpioPinAccess();
}
The other two methods add the Gpio Pin Access configuration described above and the subsequent channel configuration.
Channels and channel groups
private static ISignalFConfiguration AddGpioChannelGroup(this ISignalFConfiguration configuration)
{
configuration.AddGpioChannelGroup(builder =>
{
builder.SetName("GPIO")
.SetDeviceBinding("GPIOController")
.AddGpioChannel(channelBuilder =>
{
channelBuilder.SetName("GPIO17")
.SetChannelOptions(new GpioChannelOptions
{
DriveMode = EGpioPinDriveMode.Output,
SharingMode = EGpioSharingMode.Exclusive,
PinNumber = 17
});
})
.AddGpioChannel(channelBuilder =>
{
channelBuilder.SetName("GPIO18")
.SetChannelOptions(new GpioChannelOptions
{
DriveMode = EGpioPinDriveMode.Output,
SharingMode = EGpioSharingMode.Exclusive,
PinNumber = 18
});
})
.AddGpioChannel(channelBuilder =>
{
channelBuilder.SetName("GPIO22")
.SetChannelOptions(new GpioChannelOptions
{
DriveMode = EGpioPinDriveMode.Output,
SharingMode = EGpioSharingMode.Exclusive,
PinNumber = 22
});
})
.AddGpioChannel(channelBuilder =>
{
channelBuilder.SetName("GPIO27")
.SetChannelOptions(new GpioChannelOptions
{
DriveMode = EGpioPinDriveMode.Output,
SharingMode = EGpioSharingMode.Exclusive,
PinNumber = 27
});
});
});
return configuration;
}