Laundry card identification

General
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Hey seeing this post in 2026 - new to Bus Pirate and looking for some pointers on my first project, and this popped up when I searched “laundry”. I have a laundry card with a chip that looks like the blank 24C02 shipped with my Bus Pirate 5, but when I run a scan on it, it isn’t detected. I’ve updated firmware to most recent, tried to make sure the card is seated right, etc. I believe that the chip may be a 24C01 despite looking the same as the 24C02 because I was able to read and dump (just not able to write) 128 hex bytes using I2C protocol and ACR39U-UF smart reader from amazon. Any thoughts on next steps? Can also give more info on what else I’ve tried. sorry if this isn’t allowed in this forum!

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1-Wire mode updates
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Welcome to the forum. I moved this post to a separate topic because it was attached to a 1 wire post.

What steps have you tried so far? Here is a detailed walk through to deal with the 24c02 type cards. You need to:

  • Enter I2C mode
  • W 5 to enable power
  • P to enable pullups
  • scan to look for the I2C address.

If you don’t see an I2C address, then check the card is in the read the correct way (chip pointed up).

If it is a simple 24C02 then there shouldn’t be any write protection.

More common for laundry cards is the sle4442, which you can probe from 2wire mode using the sle4442 command. These cards can be read freely, but require a password to write. You only get three tries and then the card destroys itself.

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Question does the three tries count reset on success. I.e. bad password twice. Good password on third attempt to reset counter.

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Correct. There are three bits and you select one available bit with each attempt. When the password is correct they all reset:

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Thanks for the reply. I’ll walk through everything I’ve done so far with card images here: https://imgur.com/a/oNurJu3 (left is SLE4442, middle is 24C02, right is mine which is unidentified, but looks like the 24C02 to me)

  1. bought the ACR39U-UF smart reader. was able to dump the card’s hex bytes at a few different states and saw there were 128 bytes, but not able to write.
  2. got the bus pirate 5. followed the tutorial with the included blank 24C02, was able to do everything in the tutorial
  3. Put my own card into the bus pirate and followed the same steps from tutorial. i intended to change the read to just 128 bytes from the 256 in the tutorial, but the scan step didn’t register that there was any I2C addresses even when the card was in the reader. tried reseating the card multiple times, but no success
  4. Tried to probe from 2wire mode using that tutorial. first used the included blank sle4442 card and everything worked, but same issue happened that it didn’t register that there was even a card inside the scanner.

Good learning experience so far but wondering if i’m completely out of options for next steps

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What I2C address does the USB reader use? Does it give any card info?

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Have you tried the default address? 0x50<<1?

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i don’t have the USB reader from amazon anymore, but i remember it didn’t give info about the chip when i tried to figure out what kind of chip it was. here’s the commands i tried with the card and card adapter all plugged in:

I2C>scan

Found 0 addresses, 0 W/R pairs.

I2C> [0xA0]

I2C START

TX: 0xA0 NACK

I2C STOP

I2C> [0xA0 0x00 [0xA1 r:16]

I2C START

TX: 0xA0 NACK 0x00 NACK

I2C REPEATED START

TX: 0xA1 NACK

RX: 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK

0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF ACK 0xFF NACK

I2C STOP

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9

The scan calls every I2C address and looks for an acknowledgement. There are rare cases where i2c chips dont respond, but im not sure how the usb reader would find the card if it doesn’t have a fixed address.

Are the two switches pushed towards VDD and GND? That makes sure the card has proper power.

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Ate you sure the pull up resistors are on? Oxff with ack means nothing is pulling high or the chip is indeed responding but saying its blank.

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i think it likely has a fixed address, but i’m not sure what that is or why its not responding. SW1 is pushed towards VOUT and SW2 is pushed toward GND. I turned on the pull-up resistors with the P command

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You’re using less than 10khz speed and 5 volts power? I2c is a dead simple 70 year old protocol so its weird if it doesn’t acknowledge its address. But in your example ever bit is acknowledged so something is holding the line low during the 9th bit. If the demo cards work OK im not really sure what to do next. If you had the usb reader you could use the bus pirate logic analyzer to see the bus activity and we could debug from there.