Re: [Amforth] TWI - 7segment display Gravitech.us

[Erich W. <ew....@na...>]

Hi Jan,


On 06/02/2012 07:33 PM, Jan Kromhout wrote:
> Dear Erich,
> I have done what you wrote, seems to work.
Very good!

 > But when I look to te code of twi.frt I see
> some strange thing, or missing sommething.
> When I look into the code never is sending
> the address in twi.start \ send start condition
> : twi.start ( -- )
>      [ 1 7 lshift
>        1 5 lshift or
>        1 2 lshift or ] literal
>      TWCR c!
>      twi.wait
> ;
 >
> Where should I put the address?


The address is just the first byte to be transfered.
I use the following functions to send/receive n Byte to/from
some address. Feel free to recycle them:

\ send n bytes to addr
: >i2c ( x1 .. xN.msB N addr -- )
   twi.start
   twi.tx    \ uses addr
   0 do      \ uses N
     twi.tx  \ uses xN .. x1
   loop
   twi.stop
;

: <i2c ( N addr -- xN.msB .. x1 )
   twi.start
   1+ twi.tx \ uses addr
   1- dup 0 > if
     0 do twi.rx loop
   else
     drop
   then
   twi.rxn
   twi.stop
;

As you can see, the first call to twi.tx sends the addr.


If you have not downloaded the datasheet of your controller
from atmel.com, please do so. I know, these datasheets are
rather intimidating at first, however, they do include a lot
of information, e.g. how to set the bits in TWCR and their
meaning. I strongly suggest to consult the datasheet often.
You will learn to read it. And amforth will let you access
the registers and bits easily.

Cheers,
Erich