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Posted: **Thu Jun 13, 2013 5:15 pm**

Hi to all,

I wished to measure voltage on a or some analog input voltage of the Pic. But I can not configure the FVR module.

When VDD = 5V, the LED lights up well at 1.2 V. But when VDD is below the threshold is also different. Yet in the datasheet section 14.0, the voltage VDD must not change the threshold "The Fixed Voltage Reference, or FVR, is a stable,
voltage reference, independent of VDD "

What do I configure wrong?

Is anyone can help me please

thank you in advance

PS: Flowcode V5.5.2.1

Steve

Posted: **Fri Jun 14, 2013 9:38 am**

Hi Steve,

The chip your using uses ADC type 23. I would recommend that you make the mod inside the ADC CAL C file as otherwise your changes at the start of main will likely be overwritten.

The CAL file can be located inside the Flowcode folder and your looking for PIC_CAL_ADC.

You may need to copy the file out of program files first to allow you to edit it in a text editor. Scroll down to ADC type 23 and then add/change the code in the Enable_ADC function.

Let me know how your getting on.

Posted: **Sun Jun 16, 2013 9:26 pm**

Hi Benji,

I did not dare change the file type, but I did it anyway.

I changed as a result :

Code: Select all

#ifdef MX_ADC_TYPE_23

	MX_UINT8 * ansel_reg;					//ANSEL register pointer

	void FC_CAL_Enable_ADC (MX_UINT8 Channel, MX_UINT8 Conv_Speed, MX_UINT8 Vref, MX_UINT8 T_Charge)
	{
		adcon1 = (Conv_Speed & 0x07) << 4;						//assign conversion rate
		
		fvrcon = 0xC2;					        //Activation du module FVR pour ADC avec référence à 2.048V (FVREN, ADFVR<1:0>)
		adcon1 = adcon1 | 0x03;				//VREF est connecté au module FVR (ADPREF<1:0>)
		adcon0 = adcon0 | 0x78;				//FVR Buffer 1 Output (CHS<4:0>)

		switch (Channel)

It works very well, the transition threshold is the same as at VDD = 5V to 3V.

Thank you for your help.

Steve

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