Serial Ports on Linux

I’m having a nightmare trying to get some after market multi port serial cards working on my PC which I have recently reconfigured as a Linux Mint 14 only PC.

The card I’m using worked perfectly under Windows, but Linux, now thats a different problem all together. After a little help from various user groups, the following command reviled:

setserial -g /dev/ttyS[0-9]* | grep -v “unknown”

/dev/ttyS4, UART: undefined, Port: 0xcc20, IRQ: 19
/dev/ttyS5, UART: undefined, Port: 0xcc28, IRQ: 19
/dev/ttyS6, UART: undefined, Port: 0xcc30, IRQ: 19
/dev/ttyS7, UART: undefined, Port: 0xcc38, IRQ: 19

As can be seen, this card is showing up as UART:undefined, so entering the following resolves this:

sudo setserial /dev/ttyS4 port 0xcc20 UART 16550A irq 19 Baud_base 115200 skip_test
sudo setserial /dev/ttyS5 port 0xcc28 UART 16550A irq 19 Baud_base 115200 skip_test
sudo setserial /dev/ttyS6 port 0xcc30 UART 16550A irq 19 Baud_base 115200 skip_test
sudo setserial /dev/ttyS7 port 0xcc38 UART 16550A irq 19 Baud_base 115200 skip_test

No to confirm, If I re-enter the above setserial commands I get:

/dev/ttyS4, UART: 16550A, Port: 0xcc20, IRQ: 19
/dev/ttyS5, UART: 16550A, Port: 0xcc28, IRQ: 19
/dev/ttyS6, UART: 16550A, Port: 0xcc30, IRQ: 19
/dev/ttyS7, UART: 16550A, Port: 0xcc38, IRQ: 19

This can be a pain, as these setserial commands need to be run at boot, which presents a different problem which I won’t mention here for now.

So all well and good, ttyS4 – ttys7 should now be working, but that would be too easy. ttys 6 & ttys7 work fine, 4 and 5 do not. So far I cannot find any reason why that should be.

So now I tried an older Rockport uPCI 4J 4 port card I had hanging about the shack, this shows:

/dev/ttyS4, UART: 16654, Port: 0xcc00, IRQ: 16
/dev/ttyS5, UART: 16654, Port: 0xcc00, IRQ: 16
/dev/ttyS6, UART: 16654, Port: 0xcc10, IRQ: 16
/dev/ttyS7, UART: 16654, Port: 0xcc18, IRQ: 16

So the first thing that leaps out at me is that the Linux Mint Kernel supports PCI serial cards, but not ISA. Probably because support for serial devices has not been maintained in favour of USB serial devices. Further, if my serial card has an IRQ of 3 or 4 then I would not have any problem, but as many after market devices use high IRQ’s to avoid conflicts with possible existing cards or motherboard devices, then this compounds my problem.

Now, I’f I add a USB to Serial converter cable, there is absolutely no problem, the throughput isn’t quite as fast as a native RS232 port, but for Amateur Radio control purposes, this difference will not be noticed.

So there we have it, I have a number of multiport serial cards I’d like to use on my Linux Mint PC which work fine in Windows but cant because Linux Mint’s Kernel doesn’t support them properly. Now I “Could” rebuild the Kernel, but I don’t think I have the ability to do that. so I may end up buying a USB to 4 Ports RS232 converter cable, and put my serial cards on eBay.

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About Dave, G8FXM

A Radio Ham, mainly interested in Six Metres.
This entry was posted in CQRLog, Linux. Bookmark the permalink.

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