Entrega hub2U4S on Linux

The Entrega hub2U4S is a 2-USB hub and 4 serial ports adapter for USB produced around the turn of the century (driver files say 1999, chips marked week 52 1998 or week 09 1999), that I can't get to work with Linux. It's a shame since it has four nice, fully level-shifted RS232 ports with really nice line driving hardware (see below) and a dedicated ez-usb microcontroller and everything. It's an expensive but nice beast.

This Entrega hub and brand is usually mentioned alongside Xircom and Intel, I guess all these companies were involved in creating the hub. People started getting annoyed because the Windows driver for this hub did not work with Windows XP.

Honestly I think it would be easier to get this to work with Linux than to get it to work with newer Windows.

Supposedly the best way to get it working is to install the old Windows driver on an old Windows machine and sniff the traffic. I can't think of anything better. We sort of get that hint from the manufacturer: they helpfully included a copy of usbview.exe with the driver files, which leads us to suspect that they were working out the protocol until the last minute and were still debugging it when they shipped the device.

Hardware

Inspecting the PCB (see image) gives the following hints about the hardware:

No less than three (3!) independent crystals for clocking: M4800KL8 (48 MHz, connected to the TI TUSB2040 USB hub), M1200KK8 (12 MHz connected to the EZ-USB microcontroller), and M0368KK8 (368 kHz, connected to the ST16C554CQ serial port adapter).
A Cypress AN2135SC "EZ-USB" USB 1.1 full speed peripheral controller. This is a special purpose SoC with an Intel 8051 processor with RAM that needs firmware to run. The firmware usually comes from an EEPROM (flash chip).
An Atmel AT24C01 2-wire (SPI) EEPROM 1 KiB. This likely contains the firmware for the hub.
A TI 84CE81K pretty unknown chip, but it appears to be a 8K ROM and 256 byte RAM package addressable over I2C. (This hint found in the 80C51-Based microcontrollers handbook from Philips, 1992, archived by bitkeepers.) I guess this contains part of the firmware as well.
A TI TUSB2040 USB hub driving the two external USB ports. Hm why just two? This supports up to four. Well mechanical limitations maybe.
The serial ports are driven by a Exar XR ST16C554CQ, which is a pretty standard 16550 UART controller, each interfaced to the line with a TI SN75LV4737A 3.3/5 V RS-232 line driver.

Driver hints

The Windows driver file etisera.inf contains a few hints:

VID 1645/PID 8001, 8003 and 8093 has one serial port
VID 1645/PID 8002 has two serial ports
VID 1645/PID 8004 (this device) has four serial ports

There does not seem to be any firmware files in the driver archive, so likely the firmware is indeed solely inside the EEPROM. This is a guess, it can also be hidden inside the driver files, and we know PID 8093 needs some kind of firmware.

Look into Linux source tree

Looing into the kernel we find a driver which may be close to what we need: drivers/usb/serial/keyspan_pda.c seem to contain the Entrega VID and some quirks for dealing with the firmware on a certain PDA adapter. It lists VID 1645/PID 8093 as "Entrega Fake ID", does this mean that we may support "our" serial ports with the same driver?

Certainly it should be possible to support PID 8001 and 8003 in the same driver, as the driver is the same for Windows. But after examining the source tree it turns out that these probably all use the one UART built into the EZUSB SoC, and download the firmware over the USB wire.

Then 8002 and 8004 are thus probably very different beasts, with flash EEPROMs and USB hubs.

lsusb -v output

The device has one interface (interface 0) but it has three altsettings, which is kind of odd. Altsetting 0 contains no endpoints, whereas altsetting 1 and 2 contain 13 endpoints each: one control/interrupt endpoint (1), three bulk IN/OUT endpoint pairs numbered 2, 4, 6 and three isochronous IN/OUT pairs numbered 8, 9, 10.

The interface and device class are (unsurprisingly) all vendor-specific.

Bus 001 Device 013: ID 1645:8004 Entrega [hex] 2U4S serial/usb hub
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.00
  bDeviceClass          255 Vendor Specific Class
  bDeviceSubClass       255 Vendor Specific Subclass
  bDeviceProtocol       255 Vendor Specific Protocol
  bMaxPacketSize0        64
  idVendor           0x1645 Entrega [hex]
  idProduct          0x8004 2U4S serial/usb hub
  bcdDevice            0.18
  iManufacturer           0
  iProduct                0
  iSerial                 0
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          218
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       1
      bNumEndpoints          13
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval              10
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x04  EP 4 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x86  EP 6 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x06  EP 6 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x88  EP 8 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x08  EP 8 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x89  EP 9 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x09  EP 9 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x8a  EP 10 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x0a  EP 10 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       2
      bNumEndpoints          13
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval              10
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x04  EP 4 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x86  EP 6 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x06  EP 6 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x88  EP 8 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0100  1x 256 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x08  EP 8 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0100  1x 256 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x89  EP 9 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x09  EP 9 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x8a  EP 10 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x0a  EP 10 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
Device Status:     0x0000
  (Bus Powered)

Getting the Entrega hub2U4S to work with Linux

Hardware

Driver hints

Look into Linux source tree

lsusb -v output