CTS pin


New member
I just learned about these pins. I wasn't making use of CTS in my program up till now, and I found something odd about my LCD. The CTS pin always returns false. I configured and connected my old LCD module to check to see if it was any different. You can see the difference below.

>>> import serial
>>> f = serial.Serial("/dev/ttyUSB0", 115200) # Old LCD
>>> f.isOpen()
>>> f.getCTS()
>>> f.close()
>>> f = serial.Serial("/dev/ttyUSB1", 115200) # New LCD
>>> f.isOpen()
>>> f.getCTS()
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CF Tech

On the CFA-632 and CFA-634, the RTS can be fed back on CTS through a jumper, but the signal is ignored by the display. See page 9 of the datasheet.

On the CFA-533, CFA-631, CFA-633 and CFA-635 the pins that would be CTS and RTS are no connects.

The CTS and RTS are left over from when really slow terminals and really slow computers connected by really slow serial could easily overflow each other.

ref: http://www.cs.utk.edu/~shuford/terminal/blum_serial_port.txt
ref: http://en.wikipedia.org/wiki/RS-232

Most new "RS-232" systems only use Rx and Tx, unless they are specifically made to talk to an old system.