tibasicc/doc/tixx_guide/linkguide/usbdevices/SilverLink_Paper.txt

			+------------------------------------------+
			| TI-GRAPH LINK USB cable (aka SilverLink) |
			|		Informations		   |
			+------------------------------------------+



Link cable characteristics:
---------------------------

- Name: 'TI-GRAPH LINK USB'
- Manufacturer: 'Texas Instruments Corporated'
- VID/PID: 0x0451/0xe001
- Firmware revision: 1.03
- Internal µC: CY7C64013 (Cypress Semiconductors)


USB related things:
-------------------

The cable is a full-speed (FS, 12Mbit/s) device, USB1.1 compliant, under a 
proprietary class. It does not fit into any existing class (HID, printer, ...)
then it requires a specific device driver.

The device uses 'Bulk' mode for data transfers. There are two bulk endpoints 
(IN & OUT) and one control endpoint (mandatory). Transfers are achieved by 
packets. The endpoints advertise a maximum packet size of 32 bytes but data
are usually transfered as 256-bytes chunks (URBs) by TI-Connect.


Ti-Connect behaviour:
---------------------

The TI-Connect software systematically do the following sequence:
	- reset both pipes (IN & OUT),
	- try to read 1024 bytes (probably for flushing IN pipe),
	- reset the pipes again (URB_FUNCTION_RESET_PIPE)
before transfering anything.
This information was got by sniffing with UsbSnoopy/SniffUSB.

The TI's driver does not use Power Management.


Link cable and/or driver behaviour:
-----------------------------------

This section aims to give some importants informations. Without them, the driver will
be working badly and/or poorly. This cable has a specific behaviour which appeared to be the 
same on both Linux & Windows.

Although the maximum packet size is 32 bytes, you can not read/write bytes as you want.

1°) reset: it's better to close and reopen driver after each transfer or 
	resets both pipes before each transfer (see TI-Connect behaviour).

2°) read: you have to systematically read an 32-bytes block even if you know that you
	just need to get 4 bytes. A shorter read will lost the other bytes.
	=> solution: bufferize reading by getting a 32 byte block and processing it.

3°) quirk: the read (Linux) or the ReadFile (Win32) function can sometimes returns with 
	neither data nor error. This quirk randomly appears in transfers but almost occurs
	when getting the TI89 ID-LIST. A guy told me it was specific to Cypress devices.
	=> solution: retry a read/ReadFile access.

[ 4°) write: you can send how many bytes you want: from 1 to 32 bytes.
	Theoritically, it is better to send a block of bytes rather than byte per
	byte. This is less CPU consuming for USB layers & OS.
	Practically, transfers are more reliable if we send byte per byte because the
	calc have enough time for replying. But, the transfer rate decreases significantly 
	(1KB/s instead of 5KB/s when sending FLASH app/os).
	Using full transfer triggers some transfer interruptions.	
	=> solution: bufferize writing by sending block at once if it's full and sending it byte per byte
		when the block is incomplete. Exception: if this block is the last one of a transfer 
		(just before switching in receive mode), send it byte per byte. ] -> not true any longer

By following these 4 rules, I got good drivers for both Linux & Windows.


Identity card (Linux log):
--------------------------

Manufacturer: Texas Instruments Incorporated
Product: TI-GRAPH LINK USB
usb.c: unhandled interfaces on device
usb.c: USB device 2 (vend/prod 0x451/0xe001) is not claimed by any active driver.
  Length              = 18
  DescriptorType      = 01
  USB version         = 1.10
  Vendor:Product      = 0451:e001
  MaxPacketSize0      = 8
  NumConfigurations   = 1
  Device version      = 1.03
  Device Class:SubClass:Protocol = 00:00:00
    Per-interface classes
Configuration:
  bLength             =    9
  bDescriptorType     =   02
  wTotalLength        = 0020
  bNumInterfaces      =   01
  bConfigurationValue =   01
  iConfiguration      =   00
  bmAttributes        =   a0
  MaxPower            =  100mA

  Interface: 0
  Alternate Setting:  0
    bLength             =    9
    bDescriptorType     =   04
    bInterfaceNumber    =   00
    bAlternateSetting   =   00
    bNumEndpoints       =   02
    bInterface Class:SubClass:Protocol =   ff:00:00
    iInterface          =   00
    Endpoint:
      bLength             =    7
      bDescriptorType     =   05
      bEndpointAddress    =   81 (in)
      bmAttributes        =   02 (Bulk)
      wMaxPacketSize      = 0020
      bInterval           =   00
    Endpoint:
      bLength             =    7
      bDescriptorType     =   05
      bEndpointAddress    =   02 (out)
      bmAttributes        =   02 (Bulk)
      wMaxPacketSize      = 0020
      bInterval           =   00
      
Author:
-------

(C) Romain Liévin, developer of TiLP & TiEmu.
July the 23th, 2005