Forums

ADC sync with PWM

Started by Bruno Tremblay March 7, 2003
Hi,

I'm trying to use the synchronization feature of the ADC with PWM on a
DSP56F805 and I don't find user manual clear on this subject. Form what I
can understand, the PWM outputs a synchronization pulse connected as an
input to the quad timer module C, input of TC2 at each reload. The output of
TC2 is connected to the ADC A sync input. At each sync pulse, the ADC start
a conversion if it isn't already in process.

From what I found (I think), the PWM always generates a sync pulse on
reload. The sync bit of the ADCR1 register must be set and the scan mode of
the ADC is triggered sequential. My biggest questions are about the settings
of the timer C. There isn't enough information in the User Manual or the
Targeting Motorola DSP56F80x Platform using the SDK.

Can someone have experience with this feature?

Bruno




RE: [motoroladsp] ADC sync with PWM

The operation is as you surmise,  the pupose of the timer C is to add a timed delay between the PWM reload, and the start of the ADC conversion. 

C2 setup is as follows:

const qt_sState quadParamC2 = {

    /* Mode = */                    qtTriggeredCount,
    /* InputSource = */             qtPrescalerDiv1,
    /* InputPolarity = */           qtNormal,
    /* SecondaryInputSource = */    qtSISCounter2Input,

    /* CountFrequency = */          qtRepeatedly,
    /* CountLength = */             qtUntilCompare,
    /* CountDirection = */          qtUp,

    /* OutputMode = */              qtDeassertOnSecondary,
    /* OutputPolarity = */          qtNormal,
    /* OutputDisabled = */          1,

    /* Master = */                  0,
    /* OutputOnMaster = */          0,
    /* CoChannelInitialize = */     0,
    /* AssertWhenForced = */        0,

    /* CaptureMode = */             qtFallingEdge,

    /* CompareValue1 = */           40,
    /* CompareValue2 = */           40,
    /* InitialLoadValue = */        0x0,

    /* CallbackOnCompare = */       { 0, 0 },
    /* CallbackOnOverflow = */      { 0, 0 },
    /* CallbackOnInputEdge = */     { 0, 0 }
};

I just open the device, and then enable it.

There is a good app note in the motorola Documentation on this topic also.

Jerry.

-----Original Message-----
From: Bruno Tremblay [mailto:b...@gentec.ca]
Sent: Friday, March 07, 2003 10:32 AM
To: m...@yahoogroups.com
Subject: [motoroladsp] ADC sync with PWM


Hi,

        I'm trying to use the synchronization feature of the ADC with PWM on a
DSP56F805 and I don't find user manual clear on this subject. Form what I
can understand, the PWM outputs a synchronization pulse connected as an
input to the quad timer module C, input of TC2 at each reload. The output of
TC2 is connected to the ADC A sync input. At each sync pulse, the ADC start
a conversion if it isn't already in process.

        From what I found (I think), the PWM always generates a sync pulse on
reload. The sync bit of the ADCR1 register must be set and the scan mode of
the ADC is triggered sequential. My biggest questions are about the settings
of the timer C. There isn't enough information in the User Manual or the
Targeting Motorola DSP56F80x Platform using the SDK.

Can someone have experience with this feature?

Bruno

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