Okay, Cant find this by searching but I am sure it has been covered before so it should be a simple answer hopefully. What I want to find out without having to buy it yet is if a usb parallel converter will work when driving a hd44 parallel based lcd display. I assume all the usb parallel device will do is emulate a parallel port and thus give me a port adress to find it on so I can configure a program like lcd smartie or the winamp plugin to be able to talk to it. The device I am looking at can be found here > Link < I already have the lcd so it should be simple enough. just wanting to know if it will work. Thanks in advance
The USB to parallel converters don't usually work with the LCDs and software. Infact I've not heard of anyone getting one to work without their own software.
Yea, I am familar with ch424's usb controller. But does this mean it is effectively a No? If anyone can tell me why so that I have a better understanding. Why would work for a parallel based printer that uses software and drivers designed for parallel and not for a character lcd with drivers and software designed to run it via parallel Does it have to do with timings or signal issues? Is it dark magic that prevents this from working?
Parallel printers use the port in a standard way, so the usb converter's driver usually only emulates this standard method (i forgot the name). LCDs use the port in a custom way and so the converter's drivers do not know how to interpret that incoming signal. It would be great if you could get a device that fully emulates the parallel port, but I haven't seen one.
What makes the printer so different from the LCD anyway. Besides of course how completely different they are. But when connected the lcd is getting data from the 8 designated data lines on a parallel port. So does a printer. And the lcd just uses a few extra lines on the port for enabling write and for lcd enable. Which amounts to nothing more than pulling a few pins high and low. There seems to be a good deal of speculation and not many people trying it?
There is almost no inforation to go on, the IEE1284 mentions 5 possible modes for the port to run in, and there is no standard USB class for a USB to IEE1284 bridge. The USB device may be set up such that you do not get any control over the pins, you simply send it a bit of data in a control, interrupt, or bulk transfer and the device generates all the signaling on it's own. On the other hand, it may take a packet as 'pin state' data allowing for direct control. But there simply is not enough information to say.
