[En-Nut-Discussion] charon II with I2C

[Harald Kipp]

Hi Joel,

As a master you need to do read/write in one go

   char wrbuf[8], rdbuf[8];
   TwMasterTransact(0x39, wrbuf, 1, rdbuf, 1, 0);

In your code &write is wrong too, because it is declared
as an array and write specifies the pointer to this array.
Btw. better avoid 'write' as a variable name.

Harald

At 13:47 23.11.2004 +0100, you wrote:
>hello,
>I am new in the programming of the CHARONII, I test dialogue I2C (PCF857AP).
>I  write without problem, but not to read  with a pointer !?  can somebody 
>explain me?
>
>  here part of my code, with < dev/twif.h >
>
>  thank you in advance
>
>Joel
>
>
>static char buff[128];
>static u_char BuffRead[8];
>
>../..
>
>void ProcessRequests(FILE * stream)
>{
>     int got, i;
>     char *cp;
>  u_char write[8];
>
>     TwInit(0x39);
>  write[0]=0x80;
>
>         for (;;) {
>
>         /*
>          * Flush output and read a line.
>          */
>         fflush(stream);
>         if (fgets(buff, sizeof(buff), stream) == 0) //lit une ligne 
> venant du stream
>             break;
>
>         /*
>          * Chop off EOL.
>          */
>         if ((cp = strchr(buff, '\r')) != 0)
>             *cp = 0;
>         if ((cp = strchr(buff, '\n')) != 0)
>             *cp = 0;
>
>         /*
>          * Ignore blank lines.
>          */
>         got = strlen(buff);
>         if (got == 0)
>             continue;
>
>
>   if (strncmp("write PCF8574AP", buff, got) == 0) {
>       fputs("write on PCF8574AP ads :0x39 led: 8 on \r\n", stream);
>      fputs("send value > ", stream);
>      write[0]=128;
>      fprintf(stream,"%d\r\n",write[0]);
>      write[0]=255-write[0]; // reverse state
>      TwMasterTransact(0x39,&write,1,0,0,500);
>      fputs("Slave State after = ", stream);
>      TwMasterTransact(0x39,0,0,BuffRead,1,500);
>       for( i=0 ; i < 1;i++) fprintf(stream,"%d\r\n",255-TWDR);  //with 
> TWDR is OK ! > value is 128
>    continue;
>   }
>
>
>   if (strncmp("read PCF8574AP ", buff, got) == 0) {
>       fputs("test read PCF8574AP  ads : 0x39  \r\n", stream);
>       fputs("Read Slave State  = ", stream);
>       for( i=0 ; i < TwMasterTransact(0x39,0,0,BuffRead,8,500) +1;i++) 
> fprintf(stream,"%d\t",255-BuffRead[i]); // !! value is 0 !!
>       continue;
>         }
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