;Get the starting address of the descriptor.
     mov A, (config_desc_table - control_read_table)
;Send the descriptor.
     jmp SendDescriptor

GetStringDescriptor:
;Use the string index to find out which string it is.
     mov A, [wValue]
     cmp A, 0h
     jz LanguageString
     cmp A, 01h
     jz ManufacturerString
     cmp A, 02h
     jz ProductString
;     cmp A, 03h
;     jz SerialNumString
;     cmp A, 04h
;     jz ConfigurationString
;     cmp A, 05h
;     jz InterfaceString
; No other strings supported
      jmp SendStall

SendDescriptor:
;The starting address of the descriptor is in the accumulator. Save it.
        mov [data_start], A
;Get the descriptor length.
        call get_descriptor_length
;Send the descriptor.
        call control_read
        ret

;Send the requested string.
;For each, store the descriptor length in data_count, then send the descriptor.
LanguageString:
     mov A, (USBStringDescription1 - USBStringLanguageDescription)
      mov [data_count], A
     mov A, (USBStringLanguageDescription - control_read_table)
      jmp SendDescriptor
ManufacturerString:     
     mov A, ( USBStringDescription2 - USBStringDescription1)
      mov [data_count], A
     mov A, (USBStringDescription1 - control_read_table)
      jmp SendDescriptor
ProductString:
     mov A, ( USBStringDescription3 - USBStringDescription2)
      mov [data_count], A
     mov A, (USBStringDescription2 - control_read_table)
      jmp SendDescriptor
;SerialNumString:
;     mov A, ( USBStringDescription4 - USBStringDescription3)
;      mov [data_count], A
;     mov A, (USBStringDescription3 - control_read_table)
;      jmp SendDescriptor
;ConfigurationString:
;     mov A, ( USBStringDescription5 - USBStringDescription4)
;      mov [data_count], A
;     mov A, (USBStringDescription4 - control_read_table)
;      jmp SendDescriptor
;InterfaceString:
;     mov A, ( USBStringEnd - USBStringDescription5)
;      mov [data_count], A
;     mov A, (USBStringDescription5 - control_read_table)
;      jmp SendDescriptor

; HID class Get Descriptor routines
;
GetHIDDescriptor:
;Send the HID descriptor.
;Get the length of the descriptor.
     mov A, (Endpoint_Descriptor - Class_Descriptor)
      mov [data_count], A
;Get the descriptor's starting address.
     mov A, ( Class_Descriptor - control_read_table)
;Send the descriptor.
      call SendDescriptor
      ret

;======================================================================
;USB support routines
;======================================================================

get_descriptor_length:
;The host sometimes lies about the number of bytes it
;wants from a descriptor.
;A request to get a descriptor should return the smaller of the number 
;of bytes requested or the actual length of the descriptor.
;Get the requested number of bytes to send
     mov A, [wLengthHi]
;If the requested high byte is >0, 
;ignore the high byte and use the firmware's value.
;(255 bytes is the maximum allowed.)
     cmp A, 0
     jnz use_actual_length
;If the low byte =0, use the firmware's value.
     mov A, [wLength]
     cmp A, 0
     jz use_actual_length
;If the requested number of bytes => the firmware's value,
;use the firmware's value.
     cmp A, [data_count]
     jnc use_actual_length
;If the requested number of bytes < the firmware's value,
;use the requested number of bytes.
     mov [data_count], A
use_actual_length:
        ret

Send0ByteDataPacket:
;Send a data packet with 0 bytes.
;Use this handshake after receiving an OUT data packet.
;Enable responding to IN packets and set Data 0/1 to Data 1.
     mov A, C0h
     iowr USB_EP0_TX_Config
;Enable interrupts.
     mov A, [interrupt_mask]
     iowr Global_Interrupt
WaitForDataToTransfer:
;Wait for the data to transfer.
;Clear the watchdog timer
     iowr Watchdog
;Bit 7 of USB_EP0_TX_Config is cleared when the host acknowledges
;receiving the data.
     iord USB_EP0_TX_Config
     and A, 80h
     jnz WaitForDataToTransfer
     ret

control_read: 
;Do a Control Read transfer.
;The device receives a Setup packet in the Setup stage,
;sends 1 or more data packets (IN) in the Data stage,
;and receives a 0-length data packet (OUT) in the Status stage.
;Before calling this routine, the firmware must set 2 values:
;data_start is the starting address of the descriptor to send,
;expressed as an offset from the control read table.
;data_count is the number of bytes in the descriptor.
     push X
;Set the Data 0/1 bit to 0.
     mov A, 00h
     mov [endp0_data_toggle], A

control_read_data_stage:
;Initialize count variables.
     mov X, 00h
     mov A, 00h
     mov [loop_counter], A

;Clear the Setup bit.
     iowr USB_EP0_RX_Status
;Check the Setup bit.
     iord USB_EP0_RX_Status
     and A, 01h
;If not cleared, another setup packet has arrived, 
;so exit the routine.
     jnz control_read_status_stage

;Set the StatusOuts bit to 1 to cause the device to automatically return
;ACK in response to a received OUT packet in the Status stage.
     mov A, 08h
     iowr USB_Status_Control
;If there is no data to send, prepare a 0-length data packet.
;(The host might require a final 0-length packet if the descriptor is 
;a multiple of 8 bytes.)
     mov A, [data_count]
     cmp A, 00h
     jz dma_load_done

dma_load_loop:
;Copy up to 8 bytes for transmitting into Endpoint 0's buffer
;and increment/decrement the various counting variables.

;Place the byte to send in the accumulator:
;(control_read_table) + (data_start).
     mov A, [data_start]
     index control_read_table
;Place the byte in Endpoint 0's buffer.
     mov [X + Endpoint_0], A
;Increment the offset of the data being sent.
     inc [data_start]
;Increment the offset of Endpoint 0's buffer.
     inc X
;Increment the number of bytes stored in the buffer.
     inc [loop_counter]
;Decrement the number of bytes left to send.
     dec [data_count]
;If the count = 0, there's no more data to load.
     jz dma_load_done
;If 8 bytes haven't been loaded into the buffer, get another byte.
;If 8 bytes have been loaded, it's the maximum for the transaction,
;so send the data.
     mov A, [loop_counter]
     cmp A, 08h
     jnz dma_load_loop

dma_load_done:
;Send the data.

;Check the Setup bit.
;If it's not 0, another Setup packet has arrived, 
;so exit the routine.
     iord USB_EP0_RX_Status
     and A, 01h
     jnz control_read_status_stage

;Set the bits in the USB_EP0_TX_Config register.
;Toggle the Data 0/1 bit.
     mov A, [endp0_data_toggle]
     xor A, 40h
     mov [endp0_data_toggle], A
;Enable responding to IN token packets.
     or A, 80h
;The low 4 bits hold the number of bytes to send.
     or A, [loop_counter]
     iowr USB_EP0_TX_Config
;Enable interrupts
     mov A, [interrupt_mask]
     iowr Global_Interrupt

wait_control_read:

;Clear the watchdog timer
     iowr Watchdog

;Wait for the data to transfer and the host to acknowledge,
;indicated by Bit 7 = 0.
     iord USB_EP0_TX_Config
     and A, 80h
;When all of the transaction's data has transferred, 
;find out if there is more data to send in the transfer.
     jz control_read_data_stage
;Find out if the host has sent an OUT packet to acknowledge 
;and end the transfer.
     iord USB_EP0_RX_Status
     and A, 02h
     jz wait_control_read

control_read_status_stage:
;The transfer is complete.
     pop X
     mov A, [interrupt_mask]
     iowr Global_Interrupt
     ret

;======================================================================
;Lookup Tables
;Contain the descriptors and the codes for status indicators.
;The firmware accesses the information by referencing a specific
;table's address as an offset from the control_read_table.
;======================================================================

control_read_table:

device_desc_table:
     db 12h          ; Descriptor length (18 bytes)
     db 01h          ; Descriptor type (Device)
     db 10h,01h      ; Complies with USB Spec. Release (0110h = release 1.10)
     db 00h          ; Class code (0)
     db 00h          ; Subclass code (0)
     db 00h          ; Protocol (No specific protocol)
     db 08h          ; Maximum packet size for Endpoint 0 (8 bytes)
     db 25h,09h      ; Vendor ID (Lakeview Research, 0925h)
     db 34h,12h      ; Product ID (1234)
     db 01h,00h      ; Device release number (0001)
     db 01h          ; Manufacturer string descriptor index
     db 02h          ; Product string descriptor index
     db 00h          ; Serial Number string descriptor index (None)
     db 01h          ; Number of possible configurations (1)
end_device_desc_table:

config_desc_table:
     db 09h          ; Descriptor length (9 bytes)
     db 02h          ; Descriptor type (Configuration)
     db 22h,00h      ; Total data length (34 bytes)
     db 01h          ; Interface supported (1)
     db 01h          ; Configuration value (1)
     db 00h          ; Index of string descriptor (None)
     db 80h          ; Configuration (Bus powered)
     db 32h          ; Maximum power consumption (100mA)

Interface_Descriptor:
     db 09h          ; Descriptor length (9 bytes)
     db 04h          ; Descriptor type (Interface)
     db 00h          ; Number of interface (0) 
     db 00h          ; Alternate setting (0)
     db 01h          ; Number of interface endpoint (1)
     db 03h          ; Class code ()                    
     db 00h          ; Subclass code ()                 
     db 00h          ; Protocol code ()
     db 00h          ; Index of string()       

Class_Descriptor:
     db 09h          ; Descriptor length (9 bytes)
     db 21h          ; Descriptor type (HID)
     db 00h,01h      ; HID class release number (1.00)
     db 00h          ; Localized country code (None)
     db 01h          ; # of HID class dscrptr to follow (1)
     db 22h          ; Report descriptor type (HID)
                     ; Total length of report descriptor
     db (end_hid_report_desc_table - hid_report_desc_table),00h

Endpoint_Descriptor:
     db 07h          ; Descriptor length (7 bytes)
     db 05h          ; Descriptor type (Endpoint)
     db 81h          ; Encoded address (Respond to IN, 1 endpoint)
     db 03h          ; Endpoint attribute (Interrupt transfer)
     db 06h,00h      ; Maximum packet size (6 bytes)
     db 0Ah          ; Polling interval (10 ms)
      
end_config_desc_table:

;----------------------------------------------------------------------
;The HID-report descriptor table
;----------------------------------------------------------------------

hid_report_desc_table:   
     db 06h, A0h, FFh      ;         Usage Page (vendor defined) FFA0
     db 09h, 01h     ;               Usage (vendor defined)
     db A1h, 01h     ;               Collection (Application)
     db 09h, 02h     ;               Usage (vendor defined)
     db A1h, 00h     ;               Collection (Physical)
     db 06h, A1h, FFh ;              Usage Page (vendor defined) 

;The input report
     db 09h, 03h     ;               usage - vendor defined
     db 09h, 04h     ;               usage - vendor defined
     db 15h, 80h     ;               Logical Minimum (-128)
     db 25h, 7Fh     ;               Logical Maximum (127)
     db 35h, 00h     ;               Physical Minimum (0)
     db 45h, FFh;                    Physical Maximum (255)
;    db 66h, 00h, 00h;               Unit (None (2 bytes))
     db 75h, 08h     ;               Report Size (8)  (bits)
     db 95h, 02h     ;               Report Count (2)  (fields)
     db 81h, 02h     ;               Input (Data, Variable, Absolute)  

;The output report
     db 09h, 05h     ;               usage - vendor defined
     db 09h, 06h     ;               usage - vendor defined
     db 15h, 80h     ;               Logical Minimum (-128)
     db 25h, 7Fh     ;               Logical Maximum (127)
     db 35h, 00h     ;               Physical Minimum (0)
     db 45h, FFh     ;               Physical Maximum (255)
;    db 66h, 00h, 00h;               Unit (None (2 bytes))
     db 75h, 08h     ;               Report Size (8)  (bits)
     db 95h, 02h     ;               Report Count (2)  (fields)
     db 91h, 02h     ;               Output (Data, Variable, Absolute)  

     db C0h          ;               End Collection

     db C0h          ;               End Collection

end_hid_report_desc_table:

;----------------------------------------------------------------------
;String Descriptors
;----------------------------------------------------------------------

;Define the strings

; string 0
USBStringLanguageDescription:
    db 04h          ; Length
    db 03h          ; Type (3=string)
    db 09h          ; Language:  English
    db 04h          ; Sub-language: US
; string 1

;The Length value for each string =
;((number of characters) * 2) + 2

USBStringDescription1:     ; IManufacturerName
    db 1Ah          ; Length
    db 03h          ; Type (3=string)
    dsu "USB Complete" ;

; string 2
USBStringDescription2:     ; IProduct
    db 16h          ; Length
    db 03h          ; Type (3=string)
    dsu "HID Sample"  ;

;string 3
;If the firmware contains a serial number, it must be unique
;for each device or the devices may not enumerate properly.
USBStringDescription3:     ; serial number

; string 4                 
;USBStringDescription4:     ; configuration string descriptor
;    db 16h          ; Length
;    db 03h          ; Type (3=string)
;    dsu "Sample HID"  ;

;string 5
;USBStringDescription5:     ; configuration string descriptor
;    db 32h          ; Length
;    db 03h          ; Type (3=string)
;    dsu "EndPoint1 Interrupt Pipe"  ;

USBStringEnd:

;----------------------------------------------------------------------
;Status information.
;The status can apply to the device or an interface or endpoint.
;An index selects the correct value.
;----------------------------------------------------------------------
get_dev_status_table:
        db      00h, 00h        ; remote wakeup disabled, bus powered
        db      02h, 00h        ; remote wakeup enabled, bus powered
get_interface_status_table:
        db      00h, 00h        ; always return both bytes zero
get_endpoint_status_table:
        db      00h, 00h        ; not stalled
        db      01h, 00h        ; stalled
get_configuration_status_table:
        db      00h             ; not configured
        db      01h             ; configured
get_protocol_status_table:
        db      00h             ; boot protocol
        db      01h             ; report protocol