Reading from Parallel LCD

[The-Kevster]

Hi,
First forum i've found which has anything to do with LCD displays so even tho I don't have a Crystalfontz display i hope you can answer my question.

I have a Noritake Itron VFD which is LCD compatiable. I've made the software myself using VB using DLportIO. I'm trying to read from the display. I send the read command and the cursor moves to the next character as it should but all i read is whatever the last command was to the parallel port. Am i missing something or is it not possible to read the LCD from the parallel port.

If its not possible could someone explain why?

Thanks alot in advance,
The Kevster

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[CF Tech]

It should be possible.

In order to do the read, you would have to put the data lines of the parallel port into their "input" state.

This is easier to say than do . To start with, your PC's BIOS & motherboard must support a bi-directional data transfer. Then if your hardware can really do it you would have to find the correct commands to sent to DLportIO to get it to put the port's data lines into input mode, and the correct register to read to get their state (probably not the same one you write to).

 

[The-Kevster]

I do understand the control ports and data ports (now) so if i knew what ports i needed to set i could do it.

Thanks for your help. At least i know its possible

 

[spock]

Well...

Sorry to spoil this, but reading the parallel port is not really possible. Not on SPP mode, anyway. The SPP mode was meant for printer connection, where there was no reason to read anything from the printer. The data lines are read-only on the 0x378 register. The data lines are accessible only through EPP or ECP mode, which are quite standardised and use their own read/write sequences, instead of controlling each bit/pin of the control register manually, which would be required as the wiring of the LCDs is non-standard.