LK404-AT Keyboard connector used with a barcode scanner

zigzak · Post by **zigzak** » Sat Jan 15, 2005 3:38 pm

Hi,
I have the LK404-AT unit - 40x4 lines with AT keyboard connector on the rear.
Background is I have removed the large AT socket from the circuit-board (as it makes the module too deep to fit in the box I want to use!) and have connected the solder points to an external PS/2 style keyboard socket on my outer box. I also have a USB/Serial converter on the end of the serial interface cable from the device so I can connect via USB to my PC.

This all works great - I can connect a standard PS/2 PC Keyboard and run a standard comms program on my PC and key presses appear as expected.

However I also have a barcode scanner of the "keyboard wedge" type - so it plugs into the keyboard socket and the keyboard then piggy-backs on this. The keyboard works fine as before - however if I attempt to scan a barcode I would expect the PC to recieve the digits of the barcode as if they had been typed on the keyboard - this is what happens if I connect the same keyboard/barcode scanner to my PCs keyboard socket!

However when connect via the LK404-AT the digits from the barcode scanner appear as garbage on the comms program screen - I thought it might have been corrupting the keycode values in some way - but I'm not sure. The only difference between keypresses on the keyboard and a scanned barcode I can see is that the barcode scanner would send its "keypresses" much more quickly. It's possible to change the "character delay" that the barcode scanner uses - anything up to about 1/2second between digits - but it doesn't seem to help?

I'm wondering if anyone else has had similar problems or has any ideas what's going wrong?

Also I notice that this module is/has been discontinued and there doesn't seem to be a direct replacement (ie. device that directly accepts a normal keyboard). Any suggestions on alternatives?

Tom · Post by **Tom** » Mon Jan 17, 2005 10:20 am

Hi David,

To answer you question, I will tell you a little bit about how a key is sensed on the unit. When a key is pressed a row and column is physically shorted, and the short will be detected by the microcontroller, and an ascii character is generated afterwards.

If you use a barcode scanner, the technology is totally different. There is no way to get a row and column to physically short together, so the barcode scanner can't work with the display.

I hope this clears things up for you.

Since the unit you are talking about is discontinued, maybe you can try using a keypad instead.

Best Regards,

zigzak · Post by **zigzak** » Mon Jan 17, 2005 1:25 pm

HI Tom,

Thanks for that. However my barcode scanner has a keyboard connector on the end of its lead and can be conencted to a PC Keyboard socket - so it effectively is a keyboard as far as the connecting device is concerened.

I was disappointed that this unit is discontinued as it seems to be the only one you did with a full keyboard connection. The application I'm using the LCD for requires a full size keyboard for data input and this was the ideal solution.

Is there any other unit that offers full keyboard connection? Or can you suggest another solution?

Bernie · Post by **Bernie** » Mon Jan 17, 2005 4:56 pm

Hello David, the LK404-AT is our only unit with the full keyboard connector capability and it is discontinued.....however, we do have some excess stock available. We will sell the LK404-AT units until the stock is depleted so please feel free to place a volume order a.s.a.p. to take care of your future needs.

Regards,
Bernadine