OpenEuphoria

Re: keyboard help

• Posted by "Cuny, David" <David.Cuny at DSS.CA.GOV> May 13, 1999
• 598 views

Bernie Ryan wrote:

> I think your peek and poke are interchanged.

You are correct; my code example shows how to read the buffer, not how to
write it. I've never actually tried writing to the buffer. Well, I've never
successfully written to it, anyway. Once I figured out that it was circular
and fairly small, I figured I had better things to do in life than to mess
with it.

> Also your peeking and poking addresses and not bytes.

Keep in mind that FIRST_INDEX *contains* a value. So to find the scanCode
for the next character in the buffer, you need to get the value out of
FIRST_INDEX and add it to KEY_BUFFER.

As I look at my example, it looks the address that I use for KEY_BUFFER is
actually off by 29 bytes. That is, the actual address of KEY_BUFFER is
probably:

    KEY_BUFFER = 1083

so the examples would then read:

    scanCode = peek( KEY_BUFFER + peek( FIRST_INDEX ) )
    keyCode = peek( KEY_BUFFER + peek( FIRST_INDEX ) + 1 )

Or perhaps more clearly:

    -- get the position of the first char in the buffer
    index = peek( FIRST_INDEX )

    -- look in the buffer for the scan code
    scanCode = peek( KEY_BUFFER + index )

    -- look in the buffer at the next byte for the key code
    keyCode = peek( KEY_BUFFER + index + 1 )

I'm not even going to hazard trying to write an example that updates the
buffers. Among other issues, you have to turn off the interrupts. Otherwise,
if the user presses a key while your routine is running, *bad* things will
happen when the interrupt kicks in and updated the buffer that you were
messing with.

All in all, I think that Ralf's solution was the cleanest.

-- David Cuny