I am using the GLK24064-25 as a RS232 display. I have configured it to receive data from a CPU UART and it prints to it just fine. I have also configured it to receive data from a Linear LTC1384 RS232 driver connected to a UART chip (Philips SCC2692) that is not working. I discovered that the CPU UART generates a +12V output signal that prints to the display fine. The Linear RS232 driver generates a +5V signal which doesn't print. I thought anything above 2V normally works for most RS232 receiving devices.
Is the display threshold above 5V so that this driver chip won't work?
Sutton
GLK24064-25 display threshold voltage - RS232
-
Paradigm
- Matrix Orbital
- Posts: 255
- Joined: Thu Sep 13, 2001 6:00 pm
- Location: Calgary, Alberta, Canada
Hi Dodge55.
Given I designed this display, this question is right up my alley
.
As of R2.0 we use the ST232EBTR on that display (if you're using an older display, let me know). It's data sheet is at:
http://www.st.com/stonline/products/lit ... t202eb.pdf
From the datasheet on the 232 side:
VIL is 0.8 to 1.2V
ViH is 1.7 to 2.4V
so yes a +5V *should* be received as a logic 1. Double check that your are falling well below 0.8V for your logic lows. Also be sure that the three 232 are jumped and the two TTL jumps are not.
If you still can't get this to work, let me know what test equipment you have and I can tell you were to probe and what to look for.
Given I designed this display, this question is right up my alley
.As of R2.0 we use the ST232EBTR on that display (if you're using an older display, let me know). It's data sheet is at:
http://www.st.com/stonline/products/lit ... t202eb.pdf
From the datasheet on the 232 side:
VIL is 0.8 to 1.2V
ViH is 1.7 to 2.4V
so yes a +5V *should* be received as a logic 1. Double check that your are falling well below 0.8V for your logic lows. Also be sure that the three 232 are jumped and the two TTL jumps are not.
If you still can't get this to work, let me know what test equipment you have and I can tell you were to probe and what to look for.
James McTavish, P.Eng
Director of Engineering
Matrix Orbital
Director of Engineering
Matrix Orbital
Re:
James,
Thanks for the quick reply. The RS232 straps on connected. That was the default condition when I got the display. It is a newer display. Just got it about 2 months ago.
I am using a Tektronic scope to look at the various signals. The signals are identical coming out of the CPU UART as well at the Linear RS232 Driver. Just the amplitudes are different. Just wanted to be sure that the display accepted +5V as a logic high.
I'll start looking elsewhere for the problem. And, yes, the logic lows are well below 0.8 volts.
Sutton
Thanks for the quick reply. The RS232 straps on connected. That was the default condition when I got the display. It is a newer display. Just got it about 2 months ago.
I am using a Tektronic scope to look at the various signals. The signals are identical coming out of the CPU UART as well at the Linear RS232 Driver. Just the amplitudes are different. Just wanted to be sure that the display accepted +5V as a logic high.
I'll start looking elsewhere for the problem. And, yes, the logic lows are well below 0.8 volts.
Sutton
GLK24064-25 display threshold voltage - RS232
James,
More troubleshooting:
If I hookup the Linear LTC1384 RS232 output to a dumb terminal, it works fine. But the same output of +5V is not registered with the display. At a +12V level, the output is displayed on the display.
Sutton
More troubleshooting:
If I hookup the Linear LTC1384 RS232 output to a dumb terminal, it works fine. But the same output of +5V is not registered with the display. At a +12V level, the output is displayed on the display.
Sutton