iPhone serial port communication

http://devdot.wikispaces.com/Iphone+Serial+Port+Tutorial

 

Requirement:
1.Jailbroken Iphone with BSD Subsystem installed (Search the web for jailbreak tutorials)
2.Iphone development toolchain for Mac OSX, Linux, Windows (Cygwin) or other OS. I use this http://code.google.com/p/winchain/ in Windows.
3.Sparkfun Ipod connector or breakout board see http://www.sparkfun.com/commerce/product_info.php?products_id=633 or http://www.sparkfun.com/commerce/product_info.php?products_id=8295
4.PC USB UART – optional, but used in this tutorial. You will need either a 3.3V level UART for PC (see http://www.sparkfun.com/commerce/product_info.php?products_id=718) or you will need an old style 12V level serial cable with a level converter like this one http://www.compsys1.com/workbench/On_top_of_the_Bench/Max233_Adapter/max233_adapter.html (see warning below)
5.A soldering iron will help you out
6.Microsoft Visual Studio – optional, but used in the source code examples for the PC serial port communication.

WARNING! Do not try to use a 12V level RS232 port for this without a level converter to ~3V, it will severely damage your Iphone or render it non-functional.

Hardware:
The Dock Port
In the Ipod/Iphone dock port, the pins we are concerned with are as follows
Pin 1
Ground
Pin 18
3.3V Power (+)
Pin 12
TX also known as Serial Transmit
Pin 13
RX also known as Serial Receive

To see a full description of all of the pins in the dock connector, see here: http://pinouts.ru/Devices/ipod_pinout.shtml

Connections: iPhone/iPod Touch RX should connect to TX of the connected device, TX to RX of the connected device, and Ground to the Ground of the connected device. If your device can be powered by a low amperage, 3.3V power source you may chose to connect PIN 18 as well and power your device directly from the iPhone/iPod Touch.

Sample Codes:

 

001	#include <stdio.h>   /* Standard input/output definitions */

002	#include <string.h>  /* String function definitions */

003	#include <unistd.h>  /* UNIX standard function definitions */

004	#include <fcntl.h>   /* File control definitions */

005	#include <errno.h>   /* Error number definitions */

006	#include <termios.h> /* POSIX terminal control definitions */

007

008	static struct termios gOriginalTTYAttrs;

009

010	static int OpenSerialPort()

011

{

012	int        fileDescriptor = -1;

013	int        handshake;

014	struct termios  options;

015

016	// Open the serial port read/write, with no controlling terminal, and don't wait for a connection.

017	// The O_NONBLOCK flag also causes subsequent I/O on the device to be non-blocking.

018	// See open(2) ("man 2 open") for details.

019

020	fileDescriptor = open("/dev/tty.iap", O_RDWR | O_NOCTTY | O_NONBLOCK);

021	if (fileDescriptor == -1)

022

{

023	printf("Error opening serial port %s - %s(%d)./n",

024	"/dev/tty.iap", strerror(errno), errno);

025	goto error;

026

}

027

028	// Note that open() follows POSIX semantics: multiple open() calls to the same file will succeed

029	// unless the TIOCEXCL ioctl is issued. This will prevent additional opens except by root-owned

030	// processes.

031	// See tty(4) ("man 4 tty") and ioctl(2) ("man 2 ioctl") for details.

032

033	if (ioctl(fileDescriptor, TIOCEXCL) == -1)

034

{

035	printf("Error setting TIOCEXCL on %s - %s(%d)./n",

036	"/dev/tty.iap", strerror(errno), errno);

037	goto error;

038

}

039

040	// Now that the device is open, clear the O_NONBLOCK flag so subsequent I/O will block.

041	// See fcntl(2) ("man 2 fcntl") for details.

042

043	if (fcntl(fileDescriptor, F_SETFL, 0) == -1)

044

{

045	printf("Error clearing O_NONBLOCK %s - %s(%d)./n",

046	"/dev/tty.iap", strerror(errno), errno);

047	goto error;

048

}

049

050	// Get the current options and save them so we can restore the default settings later.

051	if (tcgetattr(fileDescriptor, &gOriginalTTYAttrs) == -1)

052

{

053	printf("Error getting tty attributes %s - %s(%d)./n",

054	"/dev/tty.iap", strerror(errno), errno);

055	goto error;

056

}

057

058	// The serial port attributes such as timeouts and baud rate are set by modifying the termios

059	// structure and then calling tcsetattr() to cause the changes to take effect. Note that the

060	// changes will not become effective without the tcsetattr() call.

061	// See tcsetattr(4) ("man 4 tcsetattr") for details.

062

063	options = gOriginalTTYAttrs;

064

065	// Print the current input and output baud rates.

066	// See tcsetattr(4) ("man 4 tcsetattr") for details.

067

068	printf("Current input baud rate is %d/n", (int) cfgetispeed(&options));

069	printf("Current output baud rate is %d/n", (int) cfgetospeed(&options));

070

071	// Set raw input (non-canonical) mode, with reads blocking until either a single character

072	// has been received or a one second timeout expires.

073	// See tcsetattr(4) ("man 4 tcsetattr") and termios(4) ("man 4 termios") for details.

074

075	cfmakeraw(&options);

076	options.c_cc[VMIN] = 1;

077	options.c_cc[VTIME] = 10;

078

079	// The baud rate, word length, and handshake options can be set as follows:

080

081	cfsetspeed(&options, B19200);    // Set 19200 baud

082	options.c_cflag |= (CS8);  // RTS flow control of input

083

084	printf("Input baud rate changed to %d/n", (int) cfgetispeed(&options));

085	printf("Output baud rate changed to %d/n", (int) cfgetospeed(&options));

086

087	// Cause the new options to take effect immediately.

088	if (tcsetattr(fileDescriptor, TCSANOW, &options) == -1)

089

{

090	printf("Error setting tty attributes %s - %s(%d)./n",

091	"/dev/tty.iap", strerror(errno), errno);

092	goto error;

093

}

094	// Success

095	return fileDescriptor;

096

097	// Failure "/dev/tty.iap"

098

error:

099	if (fileDescriptor != -1)

100

{

101	close(fileDescriptor);

102

}

103

104	return -1;

105

}