CFA533 ATX power down


New member

We're finishing an COTS product that will use your CFA533-TFH-KU module. Our idea is to leave only the CFA533 module on the front panel, so the user can power up/down/reset the system and navigate to some custom menus.

I'm almost finishing the basic ATX support, using the CFA533-TFH-KU datasheet, I managed to make it power up and reset the host computer, the LCD follows the host power state, etc. But I have a doubt about the power down functionality: how can I just "pulse" down the ATX power signal ? From the CFA533-TFH-KU datasheet (command 28):

If POWER-ON SENSE (GPIO[1]) is high, holding the red X key for 4 seconds will pulse POWER CONTROL (GPIO[2])
for the duration specified by in data[1] or the default of 1 second. If the user continues to hold the power key down, then
the CFA533 will continue to drive the line for a maximum of 5 additional seconds. During this time the CFA533 will show

OK, that's clear enough, but when I hold the X key, how do I make it only pulse de ATX power signal ? What I'm seeing is that if I hold the X key for 4 seconds, it will assert the ATX power signal for 5 seconds (measured with a multimeter), even if I release the X key just after it displays "POWER DOWN". What ends up happening is that the computer is forced off, and that's not what I want.

What I want is that if the user keeps pressing the X key, then the CFA533 will assert the ATX power signal until the system shuts down forcibly. But if the user just presses the X key for 4 seconds, I just want the LCD to pulse the ATX power signal for the period specified in command 28.

I'm powering up the CFA533 using directly the ATX +5VSB power from the motherboard ATX connector:
  • JP8 OPEN

And I'm using command 28 like this:

  • command: 28
  • length: 3
  • data[0] = 0xF0
  • data[1] = 16
  • data[2] = 1

With these connections and this command, I'm able to power on and off the host computer, the LCD detects correctly if the host is powered on or not, etc. The only thing I can't do is to pulse the ATX power signal so the host computer shuts down correctly.

Thank you.
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.
USB LCD Displays - Graphic and Character LCDs with a Keypad