1
\$\begingroup\$

I am converting digital data into an analog signal through the RS232 PCIE card I added to my PC. I have a desire to collect data from up 8 different RS232 connections and I am looking into using an RS232 splitter to collect the 8 different signals into one port (hopefully still getting 8 COM ports though).
These were the products I was looking at, but if I can't collect data as close to real time as possible, then I will need to rethink my strategy.

Does this make data transfer slower (8 times slower since there are 8 ports through 1)?

A work around I'm considering is adding more RS232 cards to the other two PCIE slots I have (but one would have to accept 4 ports, like this card https://www.amazon.com/dp/B004WKTBHW?ref_=cm_sw_r_cp_ud_dp_MKXG8GQQF8KT56VK5CWJ)

My code has my RS232 ports set to 115200 baud and this is strictly a RS232 to RS232 connection, no USB involved.

\$\endgroup\$
7
  • 1
    \$\begingroup\$ We used to use things like this, back in the day. You'd need two. And an MCU+code to operate them. But it looks as though you are shopping on Amazon. So I'm probably of no help. \$\endgroup\$
    – jonk
    Commented Sep 9, 2022 at 22:57
  • 1
    \$\begingroup\$ "Does this make data transfer slower (8 times slower since there are 8 ports through 1)?" - Yes. What is your objection to using a handful of USB-RS232 adapters? \$\endgroup\$
    – brhans
    Commented Sep 10, 2022 at 0:36
  • 2
    \$\begingroup\$ It is unknown how the expanders work. The marketing material suggests all kinds of ways, but fails to mention how the port switching between devices is done or is this just a logical AND between all data ports. So it is unlikely you can simultaneously talk to 8 devices in any other way than having 8 COM ports on your PC. \$\endgroup\$
    – Justme
    Commented Sep 10, 2022 at 7:53
  • \$\begingroup\$ @jonk I will keep that chip in mind since I may need to get intricate to get the results I want. Shopping on Amazon is just my first attempt at a solution. I am always open to shopping on Digikey or Mouser. :) \$\endgroup\$ Commented Sep 12, 2022 at 15:07
  • 1
    \$\begingroup\$ You can change USB RS232 latency settings in your windows device manager, typically down to about 1mSec. That's a little more than 11 bytes @ 115200 baud rate. If your argument is that you don't want to have to fiddle with those settings, then have you considered that your proposed PCIe RS232 cards will have FIFO buffers in them which are likely to be at least somewhere in the 16-64 byte range, and that these are equally as likely to cause you to experience latency as USB 'packetization'? \$\endgroup\$
    – brhans
    Commented Sep 12, 2022 at 16:14

1 Answer 1

1
\$\begingroup\$

That splitter takes 1 input and outputs to 8 inputs, and each output gets the same data as the input. I doubt it does traffic control through RTS and CTS, but if it did only one device could talk at at time. That would be 115.2kbaud/8. No matter what serial device you get, you can't talk faster than roughly 115.2kbaud so splitting RS232 doesn't get you more bandwidth and only one device can talk at a time. In addition, the code would have to be modified to talk to multiple devices, and you would have to also give the devices the ability to not talk at the same time (probably by checking the hardware lines, assuming that the splitter actually passes those down the line).

If you have more than one port, (like 8 ports) then all 8 ports can talk at the same time.

\$\endgroup\$
3
  • \$\begingroup\$ Thank you for the confirmation that it would be slower and using 8 ports would be the best solution. From what I read on the splitters I was looking at, only three of lines (Rx, Tx, GND) are used, so there would be no RTS/CTS control for those 8 lines. \$\endgroup\$ Commented Sep 12, 2022 at 14:55
  • 2
    \$\begingroup\$ If you don't have RTS/CTS then you have to depend on software to tell when the line is being used, which would prove difficult if using more than one device on a port. \$\endgroup\$
    – Voltage Spike
    Commented Sep 12, 2022 at 15:22
  • \$\begingroup\$ I definitely am depending on software (Unity) right now to call/open/close the lines/COM ports. I've been using Serial.open() and Serial.close() when communicating. But all of that through one port... That is why I was hoping, digitally, more COM port would show even though it is the one physical port. \$\endgroup\$ Commented Sep 12, 2022 at 15:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.