Ubuntu

Serial port not working after upgrade to V20.04

Asked by Keefy J

I've been using GTKTerm on Ubuntu version 18 happily with a dual PCI serial RS232 card for a while. On upgrading to Ubuntu 20.04 it's stopped working. Ports seem to be found by system (ttyS4 & 5):-

$ setserial -g -v /dev/ttyS[0123456]
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
/dev/ttyS4, UART: 16650V2, Port: 0xc010, IRQ: 18
/dev/ttyS5, UART: 16650V2, Port: 0xc000, IRQ: 19

I have a loopback cable on the port and when I boot machine into windows it works fine. I have also looped back handshake lines but it still doesn't help. What's odd is GTKTerm is obviously opening the port and talking to the card as the options to toggle RTS and DTR are working (I've put a scope on the pins and they go up and down) but hitting a key in the terminal does not produce any activity on Tx pin and data applied to Rx is not displayed. Various handshaking options in GTKTerm have been tried and both ports on serial card are the same. Also tried minicom but no better and putty just bleeps and does nothing when I try to open any serial port. I am a member of dialout group.

No errors are reported anywhere. PCI serial card based on Moschip mcs9900 device. Suppliers CD with drivers for the serial card says to recompile kernel with stuff added which is beyond me and it worked before without such faff.

Any help welcome.

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actionparsnip (andrew-woodhead666) said : 		#1

What is the output of:

sudo ls -lah /dev/ttyS[0123456]

Thanks

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Keefy J (keefyj) said : 		#2

As requested. I've tried setting all users to rw and also running GKTerm as root but no difference:-

crw-rw---- 1 root dialout 4, 64 May 29 10:21 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 May 29 10:21 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 May 29 10:21 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 May 29 10:21 /dev/ttyS3
crw-rw---- 1 root dialout 4, 68 May 29 10:21 /dev/ttyS4
crw-rw---- 1 root dialout 4, 69 May 29 10:21 /dev/ttyS5
crw-rw---- 1 root dialout 4, 70 May 29 10:21 /dev/ttyS6

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actionparsnip (andrew-woodhead666) said : 		#3

Is your user in the dialout group? You can check withb

groups | grep dialout

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Keefy J (keefyj) said : 		#4

Hi,

Yep. And added myself to tty group but not sure what that is and it didn't help.

I don't think it's a permission issue. The trail I was following was there is some issues with interrupts with dual port PCI cards. The fact that I can manipulate the handshake lines suggests the port is open to me but actual reception and transmission which are probably interrupt based don't work. Trouble is, I see these issues raised elsewhere but I really understand the solutions (or if they even are actually solutions). So much for a degree in computer science....

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actionparsnip (andrew-woodhead666) said : 		#5

Worth trying. Add yourself to the group and log off and on

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Keefy J (keefyj) said : 		#6

Doesn't help but thanks anyway.

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Manfred Hampl (m-hampl) said : 		#7

"And added myself to tty group "

The name of the relevant group isn't "tty" but "dialout".

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actionparsnip (andrew-woodhead666) said : 		#8

Run:

sudo usermod -a - G dialout $USER

Log off and on then test

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Carsten Schlote (carsten-schlote) said : 		#9

I have the same problem. I'm member of the relevant groups, the HW is working on WIndows and Ubuntu 18.04.5.

With the update to 20.04 gtkterm and any other terminal programm I tried stopped working. You can receive data, but not transmit anything. You can change the state of cotnrollines.

Only the Python miniterm tool seems to be able to transmit data to the port.

So, how can gtkterm be tweaked to sent data out. Python abviously can.

Can you help with this problem?

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