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--- en:pfw:usb_cdc_driver_for_rp2040 [2025-12-27 15:38] – [Implementation example] willem
+++ en:pfw:usb_cdc_driver_for_rp2040 [2026-01-13 18:16] (current) – [The idea] willem
@@ Line 131: / Line 131: @@
 Reset setup request interrupt, read bmrequest type and do HANDLE-REQ)
-Now define the ring buffer place and structures
+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>
@@ Line 374: / 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]]