I would like to debug the kernel of my nexus 5 and I sent to a fab the design for the debu cable that uses internally a
FTDI chip that creates a
USB to serial bridge.
Since the chip is a
QFN package is a little bit annoying to solder but after some tries I done it; one of the board is seen correctly, indeed from the
kernel: [12174.440550] usb 3-14: new full-speed USB device number 5 using xhci_hcd kernel: [12174.585763] usb 3-14: New USB device found, idVendor=0403, idProduct=6001 kernel: [12174.585766] usb 3-14: New USB device strings: Mfr=1, Product=2, SerialNumber=3 kernel: [12174.585767] usb 3-14: Product: DCSD USB UART kernel: [12174.585768] usb 3-14: Manufacturer: FTDI kernel: [12174.585768] usb 3-14: SerialNumber: A600ASO8 mtp-probe: checking bus 3, device 5: "/sys/devices/pci0000:00/0000:00:14.0/usb3/3-14" mtp-probe: bus: 3, device: 5 was not an MTP device kernel: [12174.606497] usbcore: registered new interface driver usbserial kernel: [12174.606569] usbcore: registered new interface driver usbserial_generic kernel: [12174.606633] usbserial: USB Serial support registered for generic kernel: [12174.608070] usbcore: registered new interface driver ftdi_sio kernel: [12174.608128] usbserial: USB Serial support registered for FTDI USB Serial Device kernel: [12174.608173] ftdi_sio 3-14:1.0: FTDI USB Serial Device converter detected kernel: [12174.608245] usb 3-14: Detected FT232RL kernel: [12174.608427] usb 3-14: FTDI USB Serial Device converter now attached to ttyUSB0
Other two boards instead are seen as a DCSD Status LED
kernel: [11309.878562] usb 3-14: new full-speed USB device number 4 using xhci_hcd kernel: [11310.024048] usb 3-14: New USB device found, idVendor=0403, idProduct=8a88 kernel: [11310.024051] usb 3-14: New USB device strings: Mfr=1, Product=2, SerialNumber=3 kernel: [11310.024052] usb 3-14: Product: DCSD Status LED kernel: [11310.024053] usb 3-14: Manufacturer: FTDI kernel: [11310.024054] usb 3-14: SerialNumber: A101FPA7
I googled it but I haven't found anything related to it.
Since two devices return the same exact descriptor I don't think it's an error of transmission but something else, anyone has idea of what can cause this behaviour?
P.S: The chip has been bought from aliexpress so I can't say are original.
As indicated by the solution, the chip was reprogrammed.
BTW thanks to the comment of @pjc50 I looked for a way of rewriting the EEPROM: on a Debian system you can install
ftdi-eeprom and after that you have to write a configuration file with the desired
vendor_id=0x0403 # Vendor ID product_id=0x6001 # Product ID
and then use the program to reflash the chip
$ sudo ftdi_eeprom --device i:0x0403:0x8a88 --flash-eeprom ftdi.conf
ftdi.conf is the name of the configuration file described above).
Now I have the device correctly indentified by the kernel.