This is a compact and universal MSP430 USB CDC driver. Every effort has been made to make it portable.

• Initialising the USB hardware on the RP2040.
• Receiving and responding to setup packets from the host (PC). This determines which driver the OS will load.
• If the host is satisfied with the setup, then sending and receiving data packets may start.

hex
Function: DEVICE-DECRIPTOR \ 18 bytes
12 c, 01 c, 10 c, 01 c, ( 1.10 ) EF c, 02 c, 01 c, 40 c, 66 c, 66 c, ( 6666 )
10 c, 66 c, ( 6610 ) 00 c, 01 c, ( vsn 1.00 ) 00 c, 02 c, 00 c, 01 c,  align

Function: CONFIGURATION-DESCRIPTOR \ 9 or 75 bytes
9 c,  2 c,  4B c,  0 c,  2 c,  1 c,  0 c,  80 c,  FA c, \ Maximum power = 500mA
8 c,  0B c,  0 c,  2 c,  2 c,  2 c,  1 c,  0 c,         \ Interface Association Descriptor - CDC 0
9 c,  4 c,  0 c,  0 c,  1 c,  2 c,  2 c,  1 c,  0 c,    \ Interface 1: Control - 1 - 0 -
5 c,  24 c,  0 c,  10 c,  1 c, ( CDC vsn 1.10 )         \ CDC Header functional
5 c,  24 c,  1 c,  0 c,  1 c,                           \ CDC Call management functional
4 c,  24 c,  2 c,  2 c,                                 \ CDC ACM functional ( two commands )
5 c,  24 c,  6 c,  0 c,  1 c,                           \ CDC Union functional ( one interface )
7 c,  5 c,  81 c,  3 c,  8 c,  0 c,  10 c,              \ Endpoint 1 IN descriptor
9 c,  4 c,  1 c,  0 c,  2 c,  0A c,  0 c,  0 c,  0 c,   \ Interface 2: DATA
7 c,  5 c,  82 c,  2 c,  40 c, 0 c,  0 c,               \ Endpoint 2 IN descriptor
7 c,  5 c,  3 c,  2 c,  40 c, 0 c,  0 c,  align         \ Endpoint 3 OUT descriptor

decimal
Function: USB-STATE  0 ,           \ Hold current USB state in first half word: 3 = ready
                                   \ In second half word are memory for the 900/880 requests
          4 c, 3 c, 9 c, 4 c,      \ English/US = language ID
          115200 ,  0 c,  0 c,  8 c,  align  \ Line data: 115k2, Stop bits, Parity, Data bits

hex
Function: START-USB     ( -- )  \ Initialise the RP2040 USB hardware
    1000000  4000C000           \ Bit-24 mask & Reset register
    2dup **bis  2dup **bic      \ Restart USB
    begin  2dup 8 + bit** until \ Wait until USB is ready
    2drop 50100000 1000 false fill \ Erase USB ram
    00000009  50110074  !       \ USB_USB_MUXING    Softcon, to PHY
    0000000C  50110078  !       \ USB_USB_PWR       VBUS overide & detect enable
    00000001  50110040  !       \ USB_MAIN_CTRl     Enable controller
    20000000  5011004C  !       \ USB_SIE_CONTROL   Enable End Point 0 interrupt
    false     50110000  !       \ Respond to address 0 on initial setup
    00011010  50110090  !       \ USB_INTE          Enable 3 interrupts
    AC000180  50100008  !       \ init COMM endpoint in buffer 1
    A8000200  50100010  !       \ init SEND endpoint in buffer 2
    A8000280  5010001C  !       \ init RECV endpoint out buffer 3
    00010000  5011204C  ! ;     \ USB_SIE_CONTROL   Enable pull up