Implement Serial.availableForWrite() for serial emulation

PaulStoffregen · Jan 27, 2024 · dd6aa84 · dd6aa84
1 parent 9a0eef6
commit dd6aa84
Showing 1 changed file with 9 additions and 1 deletion.
diff --git a/teensy4/usb_seremu.c b/teensy4/usb_seremu.c
@@ -304,7 +304,15 @@ int usb_seremu_write(const void *buffer, uint32_t size)
 
 int usb_seremu_write_buffer_free(void)
 {
- return 1;
+ uint32_t sum = 0;
+ tx_noautoflush = 1;
+ for (uint32_t i=0; i < TX_NUM; i++) {
+ if (i == tx_head) continue; // never promise current buffer, might autoflush
+ if (!(usb_transfer_status(tx_transfer + i) & 0x80)) sum += SEREMU_TX_SIZE;
+ }
+ asm("dsb" ::: "memory");
+ tx_noautoflush = 0;
+ return sum;
 }
 
 void usb_seremu_flush_output(void)