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--- en:pfw:usb_cdc_driver_for_rp2040 [2025-12-27 14:59] – [Pseudo code] willem
+++ en:pfw:usb_cdc_driver_for_rp2040 [2026-01-13 18:16] (current) – [The idea] willem
@@ Line 98: / Line 98: @@
 Function: SETUP>   ( a u -- )
 Handle the answer data  packet 'a' 'u' for all setup packages
+When done wait for a ZLP from the host to signal a correct answer
 Function: XTABLE
-...
+    Define an execution table entry for '+n' request actions
+    Define:  ( +n "name" -- )
+        Create a table with "name" for '+n' actions
+    Action:  ( request -- )
+        Execute the action for 'request' or generate a stall
+        when the 'request' is not available
+Function: ZLP>     ( -- )
+Send a zero length package through endpoint zero. This is used
+to signal the handling of a request that sends no data back
+Define four action in front that leave their execution tokens on the stack
+action xt
+action xt
+action xt
+action xt
+Function: HANDLE-SETUP ( req0 .. req3 4 -- )
+action xt
+A1 action xt
+action xt
+action xt
+action xt
+action xt
+action xt
+Function: HANDLE-REQ)  ( req0 .. req6 7 -- )
+Function: HANDLE-REQ   ( -- )
+Reset setup request interrupt, read bmrequest type and do HANDLE-REQ)
+Function: #L           ( -- +n )
+Ring buffer size, must be a power of two
+Function: #R           ( -- +n )
+this is equal to #L - 1
+Function: #RX          ( -- +n )
+Leave number of characters in receive buffer
+Function: #TX          ( -- +n )
+Leave number of characters in transmit buffer
+Function: >RX          ( c -- )
+Store character 'c' in RX ring buffer
+Function: >TX          ( c -- )
+Store character 'c' in TX ring buffer
+Function: RX>          ( -- c )
+Read character 'c' from RX ring buffer
+Function: TX>          ( -- c )
+Read character 'c' from TX ring buffer
+Function: IFLAG
+Reserve one cell space for receive interrupt flag
+Function: ENDPOINTS    ( -- )
+Handle EP1 & EP3 endpoints, save received data interrupt flag in IFLAG
+Release all interrupt flags
+Function: REQUESTS     ( -- )
+Handle all USB interrupts, that are the USB bus reset, setup requests & endpoints
+Function: USB-HANDLER  ( -- )
+Handle the receiving of the RX data using iFLAG and use the low level USB
+ACK/NAK handshake to move data from an endpoint to the RX ring buffer in a controlled way.
+Handle the transmitting of TX data, but only when a connection is made. Before filling
+the TX endpoint check if the previous data packet was sent too.
+Function: USB-KEY?     ( -- flag )
+Leave true flag when there is data in the RX ring buffer, otherwise false
+Call the USB-HANDLER once too
+Function: USB-KEY      ( -- c )
+Leave character 'c' when there is data in the RX ring buffer
+Call the USB-HANDLER waiting for space in the RX ring buffer
+Function: USB-EMIT     ( c -- )
+Store character 'c' when there is space in the TX ring buffer
+Call the USB-HANDLER waiting for space in the TX ring buffer
+Function: USB-ON
+Initialise the USB DPRAM, call START-USB, clear USB-STATE & IFLAG
+finally initialse the KEY?, KEY and EMIT vectors of the used system.
 </code>
-===== Implementation example =====
+===== Generic Forth implementation example =====
 <code forth>
@@ Line 341: / Line 422: @@
 </code>
+===== Implementations =====
+[[https://github.com/WillemOuwerkerk/noForth-T-hardware-examples-RP2040/tree/main/USB-CDC|Different noForth implementations for the USB-CDC driver]]