2 replies to this topic

[Novice Alex]

Hi Guys,

I am trying to setup a PWM to generate constant pulse for my monitoring project.
Below are the codes.

Public WithEvents Supply As InterruptPort
Public PWM_Supply As New SecretLabs.NETMF.Hardware.PWM(Pins.GPIO_PIN_D5)

Supply = New InterruptPort(Pins.GPIO_PIN_D0, False, Port.ResistorMode.PullUp, Port.InterruptMode.InterruptEdgeHigh)

Dim period As UInt32 = 1 * 1000 * 1000 '1 seconds
Dim duration As UInt32 = 5 * 100 * 1000 '0.5 seconds
PWM_Supply.SetPulse(period, duration)

After executing the last command "SetPulse", the below exception will be trigger
A first chance exception of type 'System.InvalidOperationException' occurred in Microsoft.SPOT.Hardware.PWM.dll

Can anyone highlight the problem in this declaration?
Thanks in advance.

Regards,
Novice Alex

[CW2]

I have not really verified that, but I don't think PWM is able to handle such long pulses. It is usually used for pulses that have duration of microseconds or milliseconds. You could use a timer instead.

[Victor M.]

Hello Alex,
The problem is the very large value of period that you are using in your code. I don't know why but is could be possible because this PWM is a hardware PWM and the comparator register have a limit size. This code is working well:

Public WithEvents Supply As InterruptPort

	Sub Main()
    	' write your code here
    	Dim PWM_Supply As New SecretLabs.NETMF.Hardware.PWM(Pins.GPIO_PIN_D5)
   	

    	'Supply = New InterruptPort(Pins.GPIO_PIN_D0, False, Port.ResistorMode.PullUp, Port.InterruptMode.InterruptEdgeHigh)

    	Dim period As UInt32 = 1 * 1000 * 10  '1 seconds
    	Dim duration As UInt32 = 5 * 100 * 10 '0.5 seconds
    	PWM_Supply.SetPulse(CType(period, UInteger), CType(duration, UInteger))
	End Sub

[]s,
Victor