question on 1-wire ibutton.

Hello.

I am working with 1-wire DS1990A serial number ibutton. I am not using DS2480 and general port is connected with ibutton probe. I have somehow done serial number reading, but it seems that too many bit error happens. sometimes whole 8 byte frame is read as all 1. and generally there is 1 bit error in frame and error frame happens once in about 10 frame. All error is that there is 1 where 0 should be read. but opposite does not happen. I have changed various delay parameter and frequency of error seems to change but I couln't perfectly. Please inform me how to solve this problem

Thanks.

Reply to
JY Kim
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JY Kim schrieb:

a) Check the physical layer (oscilloscope) b) Check the logical layer (logic analyzer) c) RTFM

- Udo

Reply to
Udo Piechottka

Probably timing. I used to write the code for these devices in inline assembler to control the timing as tightly as possible.

Bob

Reply to
Bob

To the OP,

do you have interrupts running of your uP ??

I too have found that tight timing is necessary.

donald

Reply to
donald

To the O.P.: FWIW, you can browse my code and schematics for 1-Wire under uC/OS-II, written in 'C' (for the i8096, but concepts are portable) at:

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I found that physical layer issues dominate and by using a driver circuit that permits adjustments of voltages, thresholds and timing, debugging is simplified. Also, a scope and logic analyzer are a _must_.

Regards,

Michael

Reply to
msg

I just finished some 1-wire code. You will need a digital storage scope. This will verify the timing, pull-up, and Driver. I think a logic analyzer would be overkill.

You did not say how you are timing. You will have to disable interrupts while sending the bit pulses. Unless your interrupts are very short and you are using a hardware timer.

Are you using Standard or Overdrive clocking?

Reply to
Neil

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Reply to
Udo Piechottka

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