ds1991 1wire read/write?

hello,

i have a ds1991 ibutton. it is on a machine and it works as a counter. they told me that it comes with a 10000 shots and every time they press the the button the counter goes -1. the ds1991 i have in my hands is with 0 shot on it and my question is, can i read the memory and find where they wrote the bytes? and can i write them? at the moment i found the way to read the family,SN and CRC but i cant read data from scratchpad or subkey , it always give FF. maybe i do something wrong or i cant read them without password?

this is the results in the monitor. R=2 34 33 DF 00 00 00 1A P=1 FF FF FF FF FF FF FF FF FF CRC=C9

im not sure if the code is ok, im newbie. i just used other codes and changed some parameteres.

any suggestions?

Tell us more about the machine and why you want to "refill" the counter. Cheers!

it is an aesthetic machine. the ibutton is in the handpiece of the machine. the reason i want to "refill" it is because when it is on 0 shots left, the machine stops and i cant do my job... then i have to send the handpiece abroad to the company to refill it. the problem is that takes ALOT of days (and the cost ofcoure)

Do you have a link or description of the machine? It might need some type of service when emptied. Filling it without service might give wrong dose, etc. It might also void any guarantee. The company might be able to detect that you have tampered with it. Cheers!

i dont have description of the machine. i just know that we send only the handpiece to the company. the handpiece has 4 wires, 2 for the ibutton and 2 for the handpiece.it doesnt need any service at all (and im a techician for these machines, so if need service, i do it). the only thing they do is to refill the ibutton.

so my questions about the ibutton (ds1991) is , if i can read and write the scratchpad on this to refill it. does it require a password for it? if i reset the password to be able to write the machine will be able to read it?

mikablis: so my questions about the ibutton (ds1991) is , if i can read and write the scratchpad on this to refill it. does it require a password for it? if i reset the password to be able to write the machine will be able to read it?

Yes with the right password you can access the scratchpad memory and update it. I would guess that the machine is in control of the password. If you change that it will not recognize the hand-piece. But this is all guesses :)

Check the DS1991 datasheet for more details on the 1-Wire commands.

Cheers!

Hello I am also working on ibutton DS1922 , I have a question how recover the serial number and the family code with Arduino.

I recover the temperature and the rest but not this...

Thanks.