topic Re: ADC readings on FRDM KL25Z in Kinetis Microcontrollers

ADC readings on FRDM KL25Z

Matt85 — Sat, 08 Nov 2014 16:38:05 GMT

Hi,

I configured the ADC for the FRDM KL25Z board as in:

This is my code:

(void)AD1_Calibrate(TRUE);

for(;;) {

(void)AD1_Measure(TRUE); /* do conversion and wait for the result */

(void)AD1_GetValue16(&value); /* get the result into value variable */

}

The readings are (with the PTD5 pin connected to 3.3v):

any idea?

Thanks

Alice_Yang — Mon, 10 Nov 2014 02:28:00 GMT

Hi Matt,

1) From the waveform , it seems that it haven't input signal in ADC0_SE6b pin, I suggest you check the pin use scope;

2) I suggest that before read the result , measure the complete status , the detail code you can refer to the "help on component ";

3) You can change anther pin to try .

Hope it helps

Alice

Matt85 — Mon, 10 Nov 2014 15:29:43 GMT

Hi, thanks for your reply, I will try your suggestions.

Do you know if I need a buffer (voltage follower) at the adc input? Is it mandatory? In case it is, which P/N is suggested? Thanks

Alice_Yang — Tue, 11 Nov 2014 03:25:32 GMT

Hi Matt,

Use the convenience pin , i test use the ADC0_SE0;

I think whether need voltage follower is rely on your input analog signal , is is a stable direct current signal , it needn't voltage follower .

Hope it helps

Alice

Matt85 — Wed, 12 Nov 2014 10:10:07 GMT

Hi, P/N for part number, which op amp is recommended to interface the ADC?

I tried the example code in the help page, it still doesn't work, most probably the impedance seen at the 3.3v pin is high/very high.