Workaround not working for "Serial port name bug on fitlet2 with Atom CPU" (Linux Mint)

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David.Cross
Posts: 2
Joined: Sun Sep 05, 2021 6:52 am

Workaround not working for "Serial port name bug on fitlet2 with Atom CPU" (Linux Mint)

Post by David.Cross »

Hi,

Can't get the the mini-serial port working on fitlet2 using the temporary solution described here:
http://www.fit-pc.com/wiki/index.php/Li ... h_Atom_CPU

Have installed the temporary solution as described with no errors, and a new serial port /dev/ttyHS1 seems to have been created as expected, but when I test the serial post using a loopback connecter attached to RS232 adapter cable [ulr]https://fit-iot.com/web/product/rs232-adapter[/url] I notice the following issues:

1. UART state not as expected:
- port/interrupt 5 (expected RTS|CTS|DTR, seeing CTS)
- port/interrupt 6 (expected RTS|DTR, seeing CTS)
2. characters appear on a different UART port/interrupt (expected 6, seeing 7)
3. number of characters is different (expected tx:10 rx:10, seeing tx:2 rx:1 brk:1)

Is the serial port config correct?
Is the loopback connector config correct?

The test steps, serial ports stats/status, and RS232 loopback connector config are shown below:

root@edge-000001:~# echo "12345678" > /dev/ttyHS1

root@edge-000001:~# cat /proc/tty/driver/serial | grep -v unknown
serinfo:1.0 driver revision:
4: uart:16550A mmio:0x7FFFF10000 irq:4 tx:0 rx:0
5: uart:16550A mmio:0x7FFFF0E000 irq:5 tx:0 rx:0 CTS
6: uart:16550A mmio:0x280000000 irq:6 tx:0 rx:0
7: uart:16550A mmio:0x7FFFF0C000 irq:7 tx:2 rx:1 brk:1 CTS

root@edge-000001:~# dmesg | grep tty
[ 8.936445] dw-apb-uart.8: ttyS4 at MMIO 0x7ffff10000 (irq = 4, base_baud = 115200) is a 16550A
[ 8.956044] dw-apb-uart.9: ttyS5 at MMIO 0x7ffff0e000 (irq = 5, base_baud = 115200) is a 16550A
[ 8.976105] dw-apb-uart.10: ttyS6 at MMIO 0x280000000 (irq = 6, base_baud = 115200) is a 16550A
[ 8.996052] dw-apb-uart.11: ttyS7 at MMIO 0x7ffff0c000 (irq = 7, base_baud = 115200) is a 16550A
[ 12.143937] ttyS6 - failed to request DMA
[ 12.203922] ttyS7 - failed to request DMA

root@edge-000001:~# setserial -g /dev/tty*
/dev/ttyS0, UART: unknown, 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: 16550A, Port: 0x0000, IRQ: 4
/dev/ttyS5, UART: 16550A, Port: 0x0000, IRQ: 5
/dev/ttyS6, UART: 16550A, Port: 0x0000, IRQ: 6
/dev/ttyS7, UART: 16550A, Port: 0x0000, IRQ: 7

root@edge-000001:~# ls -l /dev/ttyS? /dev/ttyH*
-rw-r--r-- 1 root root 9 Oct 9 18:03 /dev/ttyHS1
crw-rw---- 1 root dialout 4, 64 Oct 9 17:37 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 Oct 9 17:37 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 Oct 9 17:37 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 Oct 9 17:37 /dev/ttyS3
crw-rw---- 1 root dialout 4, 68 Oct 9 17:37 /dev/ttyS4
crw-rw---- 1 root dialout 4, 69 Oct 9 17:37 /dev/ttyS5
crw-rw---- 1 root dialout 4, 70 Oct 9 17:37 /dev/ttyS6
crw-rw---- 1 root dialout 4, 71 Oct 9 17:37 /dev/ttyS7

root@edge-000001:~# cat /dev/ttyHS1
12345678

RS232 Adapter Cable D9 Male (loopback connector config)
1 - Tx (looped to Rx)
2 - RTS (looped to CTS)
3 - Rx (looped to Tx)
4 - CTS (looped to RTS)
5 - x (open)
6 - x (open)
7 - x (open)
8 - GND (open)
9 - x (open)

Any help with this much appreciated!

David.Cross
Posts: 2
Joined: Sun Sep 05, 2021 6:52 am

Re: Workaround not working for "Serial port name bug on fitlet2 with Atom CPU" (Linux Mint)

Post by David.Cross »

The serial port config issue was resolved by switching to kernel v5.8 (wiki page seems to have been updated 8th Nov 21)

The question about the mini RS232 adapter cable loopback was resolved by bench testing, and it turns out the D9 male is actually a standard connector (which appears to contradict other posts on this forum).

Mini RS232 Adapter Cable D9 Male connector (bench verified)
1 - x
2 - Rx
3 - Tx
4 - x
5 - x
6 - x
7 - RTS
8 - CTS
9 - x

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