/// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
/// <summary>
/// Enables the SPI slave device which uses a GPIO pin as a slave select.
///
/// NOTE on how this works. When using a GPIO pin as a slave select line
/// we still need to open a SPIDev device because we need a device to
/// send the data to. The way SPIDev works each spidev device is
/// fundamentally associated with a particular slave select line and
/// this cannot be changed. The GPIO line will be used as a separate
/// slave select but the spidev device specific slave select will also
/// be asserted whenever the device is writtent to.
///
/// In order to use a GPIO as a slave select you must ignore and not
/// electrically attach anything to the slave select pin the SPIDEV
/// device uses as it will be asserted on each write.
///
/// In other words, the SPIDev device is needed to shift the data in
/// and out, however you must ignore its internal slave select line
/// entirely if you wish to use GPIO based slave selects. Otherwise
/// any device attached to it will be receive every write to the
/// SPIPort no matter which GPIO slave select is also asserted.
///
/// </summary>
/// <returns>ssHandle - the handle for the Slave Device or null for fail</returns>
/// <param name="spiSlaveDeviceIn">The GPIO of the pin we use as the slave select</param>
/// <history>
/// 21 Dec 14 Cynic - Originally written
/// </history>
public SPISlaveDeviceHandle EnableSPIGPIOSlaveDevice(GpioEnum gpioEnum)
{
// get first slave device. We need to check we have one
SPISlaveDeviceHandle ssHandle = GetFirstSlaveDeviceWithFD();
// sanity check
if (ssHandle == null)
{
throw new Exception("At least one non GPIO Slave Device must be enabled first.");
}
// create a new output port
OutputPortMM gpioSlaveSelect = new OutputPortMM(gpioEnum);
// set this high by default, most modes have slave selects high and go low to activate
gpioSlaveSelect.Write(true);
// create a new slave device handle
SPISlaveDeviceHandle outHandle = new SPISlaveDeviceHandle(SPISlaveDeviceEnum.SPI_SLAVEDEVICE_GPIO, gpioSlaveSelect);
if (outHandle == null)
{
throw new Exception("Could not create GPIO based slave select device");
}
//Console.WriteLine("SPIPort GPIO Slave Device Enabled: "+ gpioEnum.ToString());
// record that we opened this slave device (so we can close it later)
openSlaveDevices.Add(outHandle);
// return the slave device handle
return(outHandle);
}
/// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
/// <summary>
/// Constructor
/// </summary>
/// <param name="spiSlaveDeviceIn">The SPI slave device</param>
/// <param name="gpioSlaveSelectIn">The GPIO output port acting as the slave select line</param>
/// <history>
/// 21 Dec 14 Cynic - Originally written
/// </history>
public SPISlaveDeviceHandle(SPISlaveDeviceEnum spiSlaveDeviceIn, OutputPortMM gpioSlaveSelectIn)
{
spiSlaveDevice = spiSlaveDeviceIn;
gpioSlaveSelect = gpioSlaveSelectIn;
}