I install multiport serial card with WCH CH352L chipset, it has driver for Linux:

dmesg|grep ttyS

[ 1.313772] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 1.313944] serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A [ 1.314574] 00:08: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 1.314866] 00:09: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A [ 1.315268] 0000:00:07.0: ttyS2 at I/O 0xdf00 (irq = 18) is a XScale [ 1.315502] 0000:00:07.0: ttyS3 at I/O 0xe000 (irq = 18) is a XScale

setserial -g /dev/ttyS*

/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4 /dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3 /dev/ttyS2, UART: 16550A, Port: 0xdf00, IRQ: 18 - multiport card /dev/ttyS3, UART: 16550A, Port: 0xe000, IRQ: 18 - multiport card

It read nice. When try to transfer less then 17 byte it looks ok(ttyS1 and ttyS3 connected with null-modem cable):

echo "1234567890123456" > /dev/ttyS3

cat /dev/ttyS1


But when more then 16 byte:

echo "12345678901234567890" > /dev/ttyS3

cat /dev/ttyS1


echo "12345678901234567890abcdef" > /dev/ttyS3

cat /dev/ttyS1


16550A Uart FIFO has 16 byte buffer and it looks like how bytes in fifo buffer rewrite from begin because uart don't have time to send it out.

Can any help me? why it don't work fine?

asked 12 May '10, 07:48

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(14 Jun '11, 11:45) rfelsburg ♦

Two comments:


Your post implies that the ordinary serial ports in your computer work differently than your card. There is a 16-bytes buffer. Maybe the behavior you see is normal.


Install minicom

Use your null-modem cable and type to yourself. If you do Ctrl-A followed by Z it brings up the help-screen.

If you select serial-port setup you have several choices, including toggling hardware and software flow control. The main thing is -- this program will give you more to mess around with, easily! Then you can decide if your system is really working, or how it works best.


answered 13 May '10, 04:26

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accept rate: 46%

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Asked: 12 May '10, 07:48

Seen: 5,235 times

Last updated: 14 Jun '11, 11:45

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