Thread: Windows 7 Machine: Simple "C" Program to Read Keyboard Input and Write To Serial Port

I should know how to do this, but I haven't written any "C" code in years!

We have these proprietary keyboards here that have either failed or are in the process of failing. We have tried to get them repaired or replaced, to no avail. They have special graphics keys on them. They are self-powered and connect directly to a proprietary Graphics Generating "Box" that drives an HMI development environment.

We have the mappings for the keys. All we need is a simple "C" program to run on a Windows 7 Desktop that will read keyboard input (from a Logic Controls KB-1800 programmable keyboard), and then send the appropriate 2-byte sequence out the Serial Port (DB9 Connector) to the Graphics Box (DB25 connector).

I think I need to use getc(stdin) (???) ... but how is the data written out the Serial Port? Is there a special function for that (which would also set up the Comms parameters (like 9600, 8 bits, 1 stop bit, No parity).

First Key to make work: LOGIN. When this key is pressed, the HEX sequence "10 0D" is sent to the Graphics Box from the (failing) proprietary keyboard

Console Functions - Windows Console | Microsoft Docs
For getting lower level access to each keypress on your input keyboard.

Communications Resources - Win32 apps | Microsoft Docs
For writing things out to a serial port.

Some example ideas here
Serial Port Programming on Windows using Win32 API | xanthium enterprises

Salem: Thanks for those Links! I *did* get it working. Really wasn't very difficult. More just silly mistakes with the Connectors and trivial programming stuff like defining the array properly so I'm not inadvertently sending zeros. Still haven't "fleshed" all the code out ...will probably just be a massive CASE structure (and maybe some surprises coming with regard to building Displays in the EDIT Mode) ... but I can at least LOGIN now, and it's changing screens correctly ... so that's the big thing.

aghast: It's running on a Windows 7 machine. There's no "board". Just a desktop PC program to map about 170 keys and sent in short buffer to the proprietary Graphics Box.

Looks like "_getch()" is reading the keypresses and passing them immediately into the program, so that's good.

What about a Function to make the "BEEP" sound (when incorrect data is received or entered)?

Yeah, saying @someone will get your post moderated.

Salem: What do you mean "saying ATSIGNsomeone will get your post moderated"? On other Forums, "ATSIGNusername" is a "Mention" that gives that user a notification; I tried it here, and maybe that's why the post never got posted? Does it crash this system, or otherwise cause problems?

====

Here's another thing I thought of: Since this program will only be used on this proprietary system, is it possible to program a keyboard as just a straight byte numerical index from 1-255? So ... just number the keys 1-255. Then the translation could just be a lookup table ... or a table of pointers to variable-length strings (instead of a lot of gory logic). I have a programmable keyboard with 22 keys x 7 rows = 154 keys (actually less because some keys take up 2-6 "X/Y locations" ... ENTER, SPACEBAR, for example). So with over 100 more options (to a max of 255), that would surely be enough to map all the Graphics keys on the proprietary keyboard (in addition to the "standard stuff").


If I program the data strings into each key (which is what I was thinking I'd have to do), then the program gets these multi-byte strings (a byte at a time) and they have to be parsed to determine if it's one of the strings, or just a single, standard ASCII key that was pressed.

UPDATE: 2 or 3 posts have now gone POOF and disappeared, either upon initial entry, or after editing and pressing "Save Changes". Is there something I need to read to prevent this from happening? It appears the ATSIGN is taboo here ... and if you use it, your posts get auto-deleted? Is that correct?

> Is there something I need to read to prevent this from happening?
Do NOT put @ in your posts.
I don't know at what point you would level up to the point where you can put @ and it not moderate your post.
Also, saying @someone does NOT cause them to be notified in any way either.
This isn't like discord or reddit.


> and if you use it, your posts get auto-deleted? Is that correct?
> Does it crash this system, or otherwise cause problems?
No, it gets posted, but only us mods can see it.
We then have to tick a box and approve the post.
You presently have 4 posts "in moderation" at the moment, but all are effectively obsolete with your reposts.

To answer the real question, a lookup table seems a reasonable approach if you only have one style of keyboard.