CFA-635 and VB Visual Basic


New member
I bought a new CrystalFontz CFA-635 20x4 + keypad & LEDs.
I wonder, if I am going to use VB.NET , how could I display a certain message
out to the LCD screen ?
And how could I control those buttons , as well as the LEDs ?
Please help me,
Thank you very much
Your early reply is highly solicited,

PS: I really don't understand , why I send a normal string to it, it doesn't display
anything ? how could I display a message using VB.NET ?
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The reason a "normal string" doesn't work is the display uses a packet communication protocol, which you can get all the details by looking in the datasheet here: starting on page 19.

You can test your display by using the WinTest program,

There are many threads in this forum that deal with communicating with the serial/USB displays (you didn't give the complete part number, so I don't know which one you have).
You can use the forum search for "635" or "633", as they are similar, or "VB", to find threads. Here is a recent one:


New member
How could I get the keypad values ?

First of all, thank you for showing the document of LCD display screen.
I got that part working, :D
However, I didn't know how to get the values from Keypad ?
I had read the document : it has 2 packet command : 0x17 (configure key report) and 0x18 (read keypad).
I wonder : what is the procedure for getting the keypad values ?
Are we sending the packet first ? and then waiting for the keypad press and get the value ?
Could u please help me , I highly appreciate your help.
Your early reply is highly solicited,
Best regards,


New member
Could U tell me more a bit about the command for getting the report ?

I saw the command : 0x80 , is this command going to send back the report to Host ?
How are we going to see this report ?
I just wonder , how could we get the report ?
What I really need is the report content, so that , I can process these content.
However, I didn't know exactly , which command should we send at first to get the report.
Thanks once again for ur understanding,
I highly appreciated,
There is no command required to get key reports, unless you have disabled the automatic key reporting. CF Tech has already answered your question:
When you press a key, the module will send a keypad report packet to the host PC.

The host need only listen for the packet, nothing needs to be sent to the module.
The key report packet is explained on page 21 of the data sheet.

Your VB software needs to watch the port input to receive the key press/release reports. Use the 635WinTest program to see how these reports are sent from the 635.
USB LCD Displays - Graphic and Character LCDs with a Keypad