RevPi Connect ttyRS485 device not found

[jonah]

Hi,

I am having issues with the RS485 serial port on a RevPi Connect and trying to work out if it is a hardware problem. This port has been functioning correctly for several months (serial data read through the port) and now does not show up as a usb device at all:

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pi@RevPi14664:~ $ lsusb -t
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/5p, 480M
        |__ Port 1: Dev 3, If 0, Class=Vendor Specific Class, Driver=smsc95xx, 480M
        |__ Port 5: Dev 4, If 0, Class=Hub, Driver=hub/3p, 480M
            |__ Port 1: Dev 5, If 0, Class=Vendor Specific Class, Driver=smsc95xx, 480M
            |__ Port 3: Dev 6, If 0, Class=Vendor Specific Class, Driver=ftdi_sio, 12M

There should be 7 devices in total.

I'm expecting an output like this (taken from another RevPi Connect with an identical setup):

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pi@RevPi14664:~ $ lsusb -t
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/5p, 480M
        |__ Port 1: Dev 3, If 0, Class=Vendor Specific Class, Driver=smsc95xx, 480M
        |__ Port 5: Dev 4, If 0, Class=Hub, Driver=hub/3p, 480M
            |__ Port 1: Dev 5, If 0, Class=Vendor Specific Class, Driver=smsc95xx, 480M
            |__ Port 2: Dev 6, If 0, Class=Vendor Specific Class, Driver=ftdi_sio, 12M
            |__ Port 3: Dev 7, If 0, Class=Vendor Specific Class, Driver=ftdi_sio, 12M

Reviewing the kern.log file the device is not found when running through the ports of the internal usb hub, the RS485 device should appear at Port 2 of the internal usb hub (1-1.5.2):

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Aug 25 12:38:30 RevPi14664 kernel: [    2.088206] devtmpfs: mounted
Aug 25 12:38:30 RevPi14664 kernel: [    2.091628] usb 1-1: New USB device found, idVendor=0424, idProduct=9514
Aug 25 12:38:30 RevPi14664 kernel: [    2.091639] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Aug 25 12:38:30 RevPi14664 kernel: [    2.092935] hub 1-1:1.0: USB hub found
Aug 25 12:38:30 RevPi14664 kernel: [    2.093109] hub 1-1:1.0: 5 ports detected
Aug 25 12:38:30 RevPi14664 kernel: [    2.134649] Freeing unused kernel memory: 1024K
Aug 25 12:38:30 RevPi14664 kernel: [    2.410879] usb 1-1.1: new high-speed USB device number 3 using dwc_otg
Aug 25 12:38:30 RevPi14664 kernel: [    2.541373] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00
Aug 25 12:38:30 RevPi14664 kernel: [    2.548785] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Aug 25 12:38:30 RevPi14664 kernel: [    2.559428] smsc95xx v1.0.5
Aug 25 12:38:30 RevPi14664 kernel: [    2.623332] random: crng init done
Aug 25 12:38:30 RevPi14664 kernel: [    2.653436] NET: Registered protocol family 10
Aug 25 12:38:30 RevPi14664 kernel: [    2.667134] smsc95xx 1-1.1:1.0 eth0: register 'smsc95xx' at usb-3f980000.usb-1.1, smsc95xx USB 2.0 Ethernet, c8:3e:a7:01:25:9f
Aug 25 12:38:30 RevPi14664 kernel: [    2.682613] ip_tables: (C) 2000-2006 Netfilter Core Team
Aug 25 12:38:30 RevPi14664 kernel: [    2.770860] usb 1-1.5: new high-speed USB device number 4 using dwc_otg
Aug 25 12:38:30 RevPi14664 kernel: [    2.901523] usb 1-1.5: New USB device found, idVendor=0424, idProduct=9512
Aug 25 12:38:30 RevPi14664 kernel: [    2.910171] usb 1-1.5: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Aug 25 12:38:30 RevPi14664 kernel: [    2.923684] hub 1-1.5:1.0: USB hub found
Aug 25 12:38:30 RevPi14664 kernel: [    2.933380] hub 1-1.5:1.0: 3 ports detected
Aug 25 12:38:30 RevPi14664 kernel: [    3.260886] usb 1-1.5.1: new high-speed USB device number 5 using dwc_otg
Aug 25 12:38:30 RevPi14664 kernel: [    3.391395] usb 1-1.5.1: New USB device found, idVendor=0424, idProduct=ec00
Aug 25 12:38:30 RevPi14664 kernel: [    3.391405] usb 1-1.5.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Aug 25 12:38:30 RevPi14664 kernel: [    3.394570] smsc95xx v1.0.5
Aug 25 12:38:30 RevPi14664 kernel: [    3.487261] smsc95xx 1-1.5.1:1.0 eth1: register 'smsc95xx' at usb-3f980000.usb-1.5.1, smsc95xx USB 2.0 Ethernet, c8:3e:a7:01:25:a0
Aug 25 12:38:30 RevPi14664 kernel: [    3.580873] usb 1-1.5.3: new full-speed USB device number 6 using dwc_otg
Aug 25 12:38:30 RevPi14664 kernel: [    3.738826] usb 1-1.5.3: New USB device found, idVendor=0403, idProduct=6001
Aug 25 12:38:30 RevPi14664 kernel: [    3.738839] usb 1-1.5.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Aug 25 12:38:30 RevPi14664 kernel: [    3.738847] usb 1-1.5.3: Product: FT232R USB UART
Aug 25 12:38:30 RevPi14664 kernel: [    3.738854] usb 1-1.5.3: Manufacturer: FTDI
Aug 25 12:38:30 RevPi14664 kernel: [    3.738861] usb 1-1.5.3: SerialNumber: AL04PF3L
Aug 25 12:38:30 RevPi14664 kernel: [    3.788225] i2c /dev entries driver
Aug 25 12:38:30 RevPi14664 kernel: [    3.882001] spi0.1 supply vdd-io not found, using dummy regulator
Aug 25 12:38:30 RevPi14664 kernel: [    3.882171] spi0.1 supply vdd not found, using dummy regulator
Aug 25 12:38:30 RevPi14664 kernel: [    3.980983] ks8851 spi0.1: message enable is 0

The symlink is not created to /dev/ttyRS485 from /dev/ttyUSB0 either. Only one internal usb device is shown which is the symlink to the /dev/ttyConBridge device.

I have tried rebooting the device several times and I am out of ideas to test this further, any help would be appreciated.

Thanks,
Jona

[lukas]

I agree that it looks like a hardware issue. Devices on the USB bus are auto-discovered. If they don't show up, they're likely dead.

Question is, did this happen out of the blue or was the chip somehow fried by feeding a too-high voltage through the RS485 port? The FTDI chip isn't connected directly to the RS485 port, there's a TI SN65HVD75 transceiver in-between which would have to burn through first.