Date: Fri, 9 Sep 2005 15:39:52 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: vittorio <vdemart1@tin.it> Cc: freebsd-questions@freebsd.org Subject: Re: Fwd: Re: C program to write to the com port - RESOLVED Message-ID: <20050909123952.GC7464@orion.daedalusnetworks.priv> In-Reply-To: <200509091353.49269.vdemart1@tin.it> References: <200509091353.49269.vdemart1@tin.it>
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On 2005-09-09 13:53, vittorio <vdemart1@tin.it> wrote:
>
> As a C++ absolute beginner I'm trying to compile your testssc.c file with
>
> g++ testssc.c -o testssc
> (under freebsd 5.4, gcc version 3.4.2)
It's not a C++ program. You should use `cc', not `g++'.
> SerialPort.C: In function `int main(int, char*)':
> SerialPort.C:62: error: invalid conversion from `unsigned char*' to `char*'
> SerialPort.C:62: error: initializing argument 1 of `int snprintf(char*,
> size_t, const char*, ...)'
> SerialPort.C:66: error: `err' undeclared (first use this function)
> SerialPort.C:66: error: (Each undeclared identifier is reported only once for
> each function it appears in.)
> SerialPort.C:69:3: warning: no newline at end of file
>
> Could you please help to straighten things up?
The snprintf() function is what's causing you trouble in this line:
snprintf(buf,4,"%c%c%c%c",0xff,0x00,0x01,0);
As I said to Paul, in personal email messages, when there is a structure that
the serial data has to conform too, I usually prefer using explicitly named
fields in structs, temporary buffers, and memcpy() or plain assignments
instead of printf()-family functions.
#define SERVO_CMD_MAXBUF 4
struct servo_cmd {
unsigned char sc_id;
unsigned char sc_cmd;
unsigned char sc_arg;
};
int
servo_cmd_send(struct servo_cmd *sp)
{
unsigned char buf[SERVO_CMD_MAXBUF];
buf[0] = sp->sc_id;
buf[1] = sp->sc_cmd;
buf[2] = sp->sc_arg;
buf[3] = '\0'; /* Command end char. */
...
}
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