/// <summary>
/// Calculates the prescale value from the frequency (according to <see cref="ClockSpeed"/>)
/// then writes that register, then calls <see cref="ReadFrequency"/> to update properties.
/// Note the actual frequency may differ to the requested frequency due to clock scale (rounding).
/// </summary>
/// <remarks>
/// The prescale can only be set during sleep mode. This method enters <see cref="Sleep"/> if necessary,
/// then only if the device was awake before, calls <see cref="Wake"/> afterwards. It's important not to
/// start output unexpectedly to avoid damage, i.e. if the device was sleeping before, the frequency is
/// changed without starting the oscillator.
/// </remarks>
/// <param name="frequency">Desired frequency to set in Hz.</param>
/// <returns>
/// Effective frequency in Hz, read-back and recalculated after setting the desired frequency.
/// Frequency in Hz. Related properties are also updated.
/// </returns>
/// <exception cref="ArgumentOutOfRangeException">
/// Thrown when <paramref name="frequency"/> is less than <see cref="FrequencyMinimum"/> or greater than
/// <see cref="FrequencyMaximum"/>.
/// </exception>
public int WriteFrequency(int frequency)
{
// Validate
if (frequency < FrequencyMinimum || frequency > FrequencyMaximum)
{
throw new ArgumentOutOfRangeException(nameof(frequency));
}
// Calculate prescale
var prescale = CalculatePrescale(frequency, ClockSpeed);
// Enter sleep mode and record wake status
var wasAwake = Sleep();
// Write prescale
I2cExtensions.WriteJoinByte(_hardware, (byte)Pca9685Register.Prescale, prescale);
// Read result
var actual = ReadFrequency();
// Wake-up if previously running
if (wasAwake)
{
Wake();
}
// Update related properties
PwmMsMinimum = Pca9685ChannelValue.CalculateWidthMs(frequency, 0);
PwmMsMaximum = Pca9685ChannelValue.CalculateWidthMs(frequency, Pca9685ChannelValue.Maximum);
// Return actual frequency
return(actual);
}
/// <summary>
/// Reads the prescale register and calculates the <see cref="Frequency"/> (and related properties)
/// based on <see cref="ClockSpeed"/>.
/// </summary>
/// <returns>
/// Frequency in Hz. Related properties are also updated.
/// </returns>
public int ReadFrequency()
{
// Read prescale register
var prescale = I2cExtensions.WriteReadByte(_hardware, (byte)Pca9685Register.Prescale);
// Calculate frequency
var frequency = CalculateFrequency(prescale, ClockSpeed);
// Update related properties
Frequency = frequency;
PwmMsMinimum = Pca9685ChannelValue.CalculateWidthMs(frequency, 0);
PwmMsMaximum = Pca9685ChannelValue.CalculateWidthMs(frequency, Pca9685ChannelValue.Maximum);
// Return result
return(frequency);
}
