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My PC motherboard has a built-in 2-segment LED display that displays diagnostic codes such as "00" or "AF".

I'd like to connect a microcontroller to read these codes for troubleshooting purposes, etc.

The LED display has 4 pins so I'm assuming VCC and GND which leaves two pins so maybe one pin per segment?

Is there any standard for these type of devices that could point me in the right direction?

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  • \$\begingroup\$ Can you share some photos? \$\endgroup\$ Jan 30, 2023 at 4:40
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    \$\begingroup\$ I suspect you mean a two digit display, with two seven-segment digits. You can't display "AF" with only two segments. \$\endgroup\$ Jan 30, 2023 at 4:52
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    \$\begingroup\$ With only 2 extra signals it may be an I2C interface, look up I2C communication/interface. A P/N from the display component might help verify that. \$\endgroup\$
    – Nedd
    Jan 30, 2023 at 4:58
  • \$\begingroup\$ If it is I2C (and that's the most sensible way to use two wires to send the data, since SPI would require 3 at least) you can hook up an inexpensive logic analyzer and sniff the communications (probably 3.3V). \$\endgroup\$ Jan 30, 2023 at 5:09

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It's probably SMBus, which is a variant of I2C that is commonly used inside PCs

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