Problem using RTS/CTS with USB serial

Discussion and questions about programming with Ultibo.
sbk58
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Joined: Fri Jul 21, 2017 7:48 pm
Location: Canada

Problem using RTS/CTS with USB serial

Postby sbk58 » Sat Mar 02, 2019 1:02 am

I have been unable to get the RTS/CTS handshake signals to work on both FTDI and PL2303 serial drivers.

On the PL2303 the Ultibo driver correctly reads its CTS signal and limits data transmission correctly. However the RTS signal does not handshake correctly to limit the data flow on the receive side.

The FTDI Ultibo driver does not respond to its CTS signal and will continue to transmit data when the connected device deactivates the CTS line. The RTS signal stays inactive preventing the connected device from sending data to the Ultibo device.

Has anyone else come across this issue?
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Ultibo
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Re: Problem using RTS/CTS with USB serial

Postby Ultibo » Sat Mar 02, 2019 10:47 pm

sbk58 wrote:I have been unable to get the RTS/CTS handshake signals to work on both FTDI and PL2303 serial drivers.

Both of our FTDI and PL2303 devices only have RX and TX lines exposed so we cannot test RTS/CTS but if you have hardware that supports it then it should be easy enough to resolve whatever is stopping it from working.

Do you have a simple test case available or can we create one based off something like the Ultibo serial example?

Our first priority will be to check that the devices respond correctly when setting the various options and that no errors are reported. After that we can get you to try some experiments with the different options to compare results and see if we can work out what is missing.
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sbk58
Posts: 18
Joined: Fri Jul 21, 2017 7:48 pm
Location: Canada

Re: Problem using RTS/CTS with USB serial

Postby sbk58 » Sat Mar 02, 2019 11:33 pm

Hi thanks for quick response.

I am capable of testing any changes you want to try to either the FTDI an PL2303 USB drivers. I have a meter and oscilloscope so electrical measurements are not a problem.

I can easily reproduce the problem with my current project so software testing is also not a problem.

Let me know what you would like to try...
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Ultibo
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Re: Problem using RTS/CTS with USB serial

Postby Ultibo » Mon Mar 04, 2019 10:41 pm

sbk58 wrote:Let me know what you would like to try...

Just reviewing both drivers to see if there is anything specific about the handling of RTS/CTS etc, there are a lot of supported devices for both PL2303 and FTDI some of which exhibit "unusual" behavior so if you could tell us the device ID (vendorid : productid pair) for your devices that will help to narrow which cases we are looking at.

You can normally obtain these easily from lsusb in Linux but there are also other options if you don't have a Linux installation available.

Thanks.
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sbk58
Posts: 18
Joined: Fri Jul 21, 2017 7:48 pm
Location: Canada

Re: Problem using RTS/CTS with USB serial

Postby sbk58 » Tue Mar 05, 2019 3:10 pm

I have 3 PL2303 cables and 5 FTDI devices I have attempted to use with Ultibo.

All of my PL2303 cables:
Vendor: 067b
Product: 2303

Various FTDI devices:
Vendor: 0403
Product: 6001

I used lsusb under Ubuntu 16.04 x64 system to read vendor and product Ids.

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