Problems with the communication with analog input module.

I am trying to communicate a microcontroller P89c51RD through serial port with a analog input(AI) module ICP_DAS. The AI has an own communication protocol, (send #011 and it responds to channel 1, i.e +0.065), using other languages (LabView) I have not had any problem to read the analog input.
I have made sure that the configuration of the port is correct, that the format of the sent data is adapted (string). But I do not know that it happens, because microcontroller does not receive anything.
Part of my code is this:

// Function to send command to read analog input.
bit lee_AI_ICP(void)
{   	bit send;
	char lee_ai[10]="#011";
	printf("%s\r", lee_ai);
	send=0;
	return send; }

// Part of main routine
while(1) {
	if (send&&buffer_full) {
	send=lee_AI_ICP();
	buffer_full=0; }

	if (RI&&(!buffer_full)) {
	medida[buf_cnt]=_getkey();
	buf_cnt=++buf_cnt;
	RI=0; }

	if (buf_cnt==6) {
	buffer_full=1;
	buf_cnt=0;
	send=1; }
	}