waste of time
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Last edited by stts; 03-24-2023, 02:56 PM. -
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Hi, hopefully this information is useful for everybody.
I have found 2 different simple methods of extracting the pin/password from the 750c in case of lost or forgotten situations.
My friend forgot his pin and asked me to help retrieve it.
Open the display using the directions in the thread so you have access to the PCB.
There should be a small 8 legged eeprom chip next to the stm32 MCU.
The eeprom should be labeled 24LC04.
You have 2 options depending on your ability to solder.
Option 1 is to de-solder the chip and read the data with a chip reader (see amazon pic below)
You will need to set the data to Big-endian, the pin code can be seen in the screenshot below.
It shows 1A 30. When you convert these bits to decimal, you get 26 48. The bits should be converted separately.
The 2nd option is to use a cheap logic analyzer (see amazon below)
You need to attach the clips to pins 6 and 5 of the eeprom (SDA, SCL) and GND
A 24v power supply also needs to be connected
I won't go into how to setup the logic analyzer software, there is plenty of tutorial on YouTube. You need to setup an I2C protocol.
Once set up, start the analyzer and turn on the display. You will see a short burst of data.
Filter the results to show only data and the pin will be displayed in the same hex format (as circled)
The write section refers to the location in the eeprom (7E 7D 7F)
the read lines refers to the useful data
So you only need to look for the data at 0x7E and 0x7F
1A 30
Convert the bits to decimal and you have your pin.Attached FilesLast edited by BenTen; 04-27-2023, 07:16 AM.Comment
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The 1919 lock code on my display 750c doesnt work why?Comment
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