DS1990a Trouble

[Maximilius]

Hello,

I've some trouble to read Dallas touch device (DS1990a).

This is my hardware config:
DQ on Pin_B5 tired to +5V via pullup resistor (4.7K)
µc = 18F458 @ 20MHz

I've tried first de EX_Touch.c example, but It's seem doesn't working for me!
I've also tried some snap code found on this forum but wihtout success.
How can I track some bug with 1-Wire protocole?

Any informations are welcome.

Regards,

Maximilius

[ckielstra]

Many things can be wrong.

1) Which version of the CCS compiler are you using? V3.191 to v3.202 have a bug in delay_us() with values larger than 153 (two of these in touch.c).
2) PIN_B5 is also used for Low-voltage programming. Make sure you have the fuse NOLVP set in your program.
3) Have you checked your processor to be running fine? I always test with a simple program like blinking a led every second, this way you know the oscillator is running at the correct speed, etc.

[Maximilius]

Hi ckielstra,

Thanks for your quickly response

1) I use the V3.221 version of C Compiler.
2)I've checked the fuses and NOLVP is used.
3)I've tried a blinking led @ F=1Kz and accuracy is correct.

Any others suggests?

Regards,

Maximilius

P.S.: Here's my own delay_us function than I use:
#define DELAY_1US {#asm nop nop nop nop nop #endasm} // Delay = 1µs @ Fosc = 20MHz

void delayus(int16 timeus) {
while (timeus--) {
DELAY_1US;
}
}

[ckielstra]

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