Ctrl-C

To interrupt a running system at any time and reset it to the prompt a keyboard command ctrl-c is often used. AmForth can honour such a keystroke as well. To achieve it, a small code change needs to be applied and a new hex file pair has to be flashed to the controller.

The code change affects the interrupt usart handler (drivers/usart-rx-isr.asm). Here add the 4 lines 5-8:

  lds xh, USART_DATA
  ; optional: check for certain character(s) (e.g. CTRL-C)
  ; and trigger a soft interrupt instead of storing the
  ; charater into the input queue.
  cpi xh, 3
  brne usart_rx_store
  jmp 0
usart_rx_store:
  lds xl, usart_rx_in

With this change, whenever the keyboard sends the ascii code 3 (for ctrl-c) it is catched immediately and a soft reset is made. it requires that the WANT_ISR_RX option is set to 1.