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633 Power supply control problems


New member
I seem to be having a problem controling my ATX power supply with my 633 serial display. When I hook everything up, and turn the power supply's master switch on, it will fire up the system imediatly without hitting the green check button. Holding down the red check button for any length of time will not turn the system off. If I remove the power connector from the display to the motherboard, and short the pannel switch connector, and make it shut off, then the characters will still be on the screen, but the backlight will be off. If I reconnct the power switch connector, and hit the green check, it will not turn back on. Any ideas what's going on? :confused:
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CF Tech

You need to enable the ATX power switch functionality, and save that as the 633's default boot state. From the 633's data sheet:

28: Set ATX Power Switch Functionality
This command allows the 633 to replace power and reset switches in an “ATX” compatible system. The ATX Power Switch Functionality is one of the items stored by the “4: Store Current State As Boot State” command. (So use that command if you want the 633 to continue working as the power switch :) )

There are four functions that can be enabled by this command:

KEYPAD_RESET: If POWER-ON SENSE (GPIO[1]) is high, holding the green check key for 4 seconds will pulse RESET (GPIO[3]) pin low for 1 second. During the 1-second pulse, the 633 will show “RESET”, and then the 633 will reset itself, showing its boot state as if it had just powered on. Once the pulse has finished, the 633 will not respond to any commands until after it has reset the host and itself

KEYPAD_POWER_ON: If POWER-ON SENSE (GPIO[1]) is low, pressing the green check key for 0.25 seconds will pulse POWER CONTROL (GPIO[2]) low for 1 second. During the 1-second pulse, the 633 will show “POWER ON”, then the 633 will reset itself.

KEYPAD_POWER_OFF: If POWER-ON SENSE (GPIO[1]) is high, holding the red “X” key for 4 seconds will pulse POWER CONTROL (GPIO[2]) low for 1 second. During the 1-second pulse, the 633 will show “POWER OFF”. In order for the system to look “off”, the 633 will then clear its screen. The fans will stop and the backlight will go off if the host drops the +12v supply, which would be expected. The 633 will then “sleep”, waiting for POWER-ON SENSE (GPIO[1]) to go high or a packet to be received.

LCD_OFF_IF_HOST_IS_OFF: If you have set “LCD_OFF_IF_HOST_IS_OFF” The 633 will then blank its screen to simulate its power being off any time POWER-ON SENSE (GPIO[1]) is low. The 633 will still be active (since it is powered by VSB), monitoring the keypad for a power-on keystroke and monitoring its serial connection for a packet from the host. If +12v remains active (which would not be expected, since the host is “off”), the fans and backlight will remain on at their previous settings. Once POWER-ON SENSE (GPIO[1]) goes high, the 633 will “un-blank” its display.

#define LCD_OFF_IF_HOST_IS_OFF 0x10
#define KEYPAD_RESET 0x20
#define KEYPAD_POWER_ON 0x40
#define KEYPAD_POWER_OFF 0x80
type = 28
data_length = 1
data[0]: bit mask of enabled functions
So use the following sequence of commands in 633_WinTest's "packet debugger" window:

{set command to}28: Set ATX Power Switch Functionality
{set data to}/224
{click "send packet"}

{set command to}4: Store Current State As Boot State
{no data}
{click "send packet"}
Whatever is displayed when you do the "4: Store Current State As Boot State" will become the boot screen (as well as contrast, backlight, fans, and special characters).


New member
Well, I got the reset, power on, and I think power off working just fine, however, it still automatically turns on my machine when I give it power. Is there anyway I can tell it not to do this when it first gets power?

CF Tech

The 633 is not doing it.

Usually there is a setting in the BIOS like "Auto Resume after power failure" or something along those lines. The setting is intended for computers that are supposed to be on at all times, so they will always power up when AC is applied. My guess is that is enabled on your PC.
USB LCD Displays - Graphic and Character LCDs with a Keypad


New member
Odd.. Very, very odd...

This problem only happens when I have GPIO[2] connected to my mobo's power switch WHEN I turn on the power supply's switch.

I put a 1k resistor in between GPIO[2] and my mobo's power switch, and now it seems to work time. I won't therorize as to what exactly is causing this, except that my mobo might just a bit more sensitive then other ones. (Power on after failure has been disabled the entire time, and the system does not power up after failure)

Anyway, that's all cool, however, is the screen suppost to say "POWER OFF" when it's 'off'?