The global unique serial number (ID) of an iButton is written into the chip by laser during manufacture. But now we have another way to assign new IDs to the RW1990 programmable iButtons using our serial port iButton ID writer and tm1990b programming software.
To make this job done, we need to prepare below items:
- iButton Serial Number(ID) Writer/Programmer;
- A RW1990 programmable ibutton key by iBUTTON.CC;
- The tm1990b ibutton programming software for windows(limited download);
- CRC code calculator of 8bit family code (01) and 48-bit serial number;
- A serial port cable for motherboard of desktop computers(optional)
Below is a picture of a whole set of iButton ID writer set.
The serial port ibutton ID writer and RW1990 writable ibuttons are available from our website as well as the programming software. The difficulty is the 8-bit CRC code of item 4 and it is very difficult to understand the calculation of CRC code for common users. Luckily we have tools or formula to generate the CRC given a 48-bit string and the family code. We now illustrate an online calculator name as CRC8 Calculator. All we need to do is input the ID (family code + 48-bit serial number) and then click ‘submit’ button on that link.
Take the 01 family code and 0123456789AB serial code for example, we input the string 010123456789AB on the calculator and click summit, then we get below output:
So the CRC code is 10 for the string 010123456789AB. The whole 64-bit serial ID number is 010123456789AB10.
Now back to process of assigning IDs by the programming software.
1. Launch the ibutton programming software as below(Please refer to Install iButton Copy Software TM1990B on Windows XP/7(32bit)/8(32bit)):
2. Input the new ID on the box (or you can copy and paste 010123456789AB)
3. Holding a RW1990 key on the blue dot receptor then click rdrom and the written id is show one the box (ROMID).
4. Keep holding the RW1990 ibutton key and click ‘ROMReadContinue’, until the ‘START’ is selected on the ‘TIMER INTERVAL’ field.
5. Now the process is complete. You can check with the ibutton by the OneWireViewer as below showing that now the ibutton has an ID (shown in reversed order) assigned by you.
It is really simple and the writing process should be done in seconds with the ibutton ID writer and programmer software. But can we write an ID number with an incorrect CRC cod? Well actually you can write an inconsistent ID to rw1990 ibuttons mentioned by above steps and show as below (with CRC code 11 which is not correct):
The problem is that you can’t read at all by OneWireViewer(No IDs will be show on it, including the ID of the USB adapter since it detects the CRC code is wrong on the 1-Wire bus).
And when you click ‘readrom’ by the writer software you will receive a CRC Error as below:
About iBUTTON CC
iButton CC is an Integrated High-Tech Which Includes Development, Production, Distribute and Trade. We manufacture & supply iButton, Dallas keys, iButton readers and iButton probes. We offer Chinese domestic ones as well as products by Maxim Integrated. Take a visit to our website iBUTTON.CC for more product detail.