Inconsistant serial numbers

Archiver

Greetings fellow stamp enthusiasts,

I recently bought some DS2401 Silicon Serial Numbers and I am using
a BS2p24to read them. I am getting some wierd results. Half the
DS2401s respond to the [noparse][[/noparse]$33] Read ROM command with what appears to
be the proper serial numbers starting with family code 01. The
balance of the DS2401s respond with serial numbers starting with a
family code 03 and seem to yield varing serial numbers on subsequent
reads. However, all the DS2401s respond consistantly with what
appear to be good serial numbers if I use the [noparse][[/noparse]$f0] Search ROM
command. Would any one be willing to hazard a guess at what is
wrong here?

Thanks for your help in advance.

Numbatboy2004

Archiver

Are you testing these 1-wire devices individually?
Are all of these on the same chain? if so how far apart?
Did you put a 4.7K pull-up resistor on the data line? You only need 1
pull-up. Doesn't matter how many devices you have connected together.
When you issue the "Read ROM" command ($33) are you storing the 64 bit
serial number in a 8 byte array? for example: OWIN data, 0, [noparse][[/noparse]STR
Rom_Serial_Num\8]

These are picky to power supply noise. I've had good luck with putting a
.1uF filter capacitor on the Vcc-gnd close to the device as possible. Use a
1uF cap if you have more than 16 devices on your network. another
possibility is perhaps the others are simply gone bad.



At 08:16 AM 5/16/2004, you wrote:
>Greetings fellow stamp enthusiasts,
>
>I recently bought some DS2401 Silicon Serial Numbers and I am using
>a BS2p24to read them. I am getting some wierd results. Half the
>DS2401s respond to the [noparse][[/noparse]$33] Read ROM command with what appears to
>be the proper serial numbers starting with family code 01. The
>balance of the DS2401s respond with serial numbers starting with a
>family code 03 and seem to yield varing serial numbers on subsequent
>reads. However, all the DS2401s respond consistantly with what
>appear to be good serial numbers if I use the [noparse][[/noparse]$f0] Search ROM
>command. Would any one be willing to hazard a guess at what is
>wrong here?
>
>Thanks for your help in advance.
>
>Numbatboy2004
>
>
>
>
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