/// <summary>
/// Base class constructor for any infrared oriented codec
/// </summary>
/// <param name="transmitter">A valid infrared transmitter reference</param>
/// <param name="frequency">The carrier frequency to be used</param>
/// <param name="pulseDuty">The desired pulse-duty cycle</param>
/// <remarks>
/// The pulse duty-cycle is meant to be expressed as a value from 0.0 to 1.0,
/// and is the ratio between the duration of the high-level and the pulse period
/// </remarks>
protected InfraredCodecBase(
InfraredTransmitter transmitter,
float frequency,
float pulseDuty)
{
this.Transmitter = transmitter;
//calculates the actual period for pushing out one
//ushort value, interleave including
float t_carrier = 1 / frequency;
float t_ushort = t_carrier - 2e-3f; // subtrai 2us (porque?)
//calculates the equivalent SPI frequency
//note that an "ushort" is 16 bits
uint spi_freq = (uint)(16.0f / t_ushort);
//prevent a frequency too low: seems that Netduino hangs
//when the frequency is below a certain value
if (spi_freq < 300)
{
throw new Exception();
}
this.Config = new SPI.Configuration(
Cpu.Pin.GPIO_NONE, // SS-pin (not used)
true, // SS-pin active state (not used)
0, // The setup time for the SS port (not used)
0, // The hold time for the SS port (not used)
true, // The idle state of the clock (not used)
true, // The sampling clock edge (not used)
spi_freq, // The SPI clock rate in KHz
SPI.SPI_module.SPI1 // The used SPI bus (refers to a MOSI MISO and SCLK pinset)
);
//calculate the pulse mask
int mask = 1;
for (int i = 1; i <= 16; i++)
{
if ((i / 16.0f) < pulseDuty)
{
mask = (mask << 1) | 1;
}
else
{
break;
}
}
this.PulseMask = (ushort)mask;
}
/// <summary>
/// Create a new instance of codec
/// </summary>
/// <param name="transmitter">A valid reference for the transmitter to be used</param>
public InfraredCodecSonySIRC(InfraredTransmitter transmitter)
: base(transmitter, CarrierFrequency, PulseDuty)
{
}
/// <summary>
/// Create a new instance of codec
/// </summary>
/// <param name="transmitter">A valid reference for the transmitter to be used</param>
public InfraredCodecRC5(InfraredTransmitter transmitter)
: base(transmitter, CarrierFrequency, PulseDuty)
{
//the RC-5 protocol fixes a well-defined duration for any logic bit
this.TotalPulseCount = 64;
}
