If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. If at first you don't succeed, try writing your phone number on the exam paper. Hi Anduril, First of all i would like to apologize for using colloquial language in my post. Also I am glad and appreciate you for giving feedback and suggestions regarding my post.
Yes I mean RS itself. In my program, I have defined a constant i. H and DOS. H, is just because, the program that is written for communication must be compatible to DOS environment. It is a prime requisite that, the programs will be run in the DOS environment. If I wont do that, I would have resulted in receiving random sized data at the receiver, even if the sender sends complete data.
I tried to search other libraries and function, but I am not succeeded in searching. Could any one please suggest some libraries or functions that works in DOS environment and uses Serial port RS as a basic communication interface for transmitting and receiving data. Thanks In advance. Regards, Chetanraj. Originally Posted by chetanraj. C99 Tutorial. I agree with Hodor, though am a little less angry about it.
And c99tutorial gave you some good advice. I suspect, however, that this is a school assignment, and you may be required to use Turbo C -- if so, I'm sorry. Your education system is doing you a disservice. I recommend you familiarize yourself with modern tools as well, so as to be prepared for the real world when you're done. Similar Threads serial communication By cbrandy in forum C Programming. Replies: 2 Last Post: , AM. Replies: 8 Last Post: , PM. ReadIntervalTimeout Specifies the maximum time interval between arrival of two bytes.
If the arrival time exceeds these limits the ReadFile function returns. ReadTotalTimeoutConstant is used to calculate the total time-out period for read operations. For each read operation, this value is added to the product of the ReadTotalTimeoutMultiplier member and the requested number of bytes.
ReadTotalTimeoutMultiplier is used to calculate the total time-out period for read operations. For each read operation, this value is multiplied by the requested number of bytes to be read. After this you have to set the values using SetCommTimeouts function. Writing data to the opened serial port is accomplished by the WriteFile function. Microcontroller Interface. The Controller waits for a character to be received and lights up the corresponding LED.
The code for interfacing MSP is available in the Github repo. We have also included code for. The connection setup is similar to the MSP Here is the screen shot of the Program writing into serial port of Windows 7 Computer.
Please note that i have changed the names of the C files in the latest release. Here is the screen shot of the Program writing into serial port of Windows 10Computer. One way to do that is to use polling where the ReadFile continuously reads from the serial port and checks for any received characters. Other way is to setup an event and let windows notify us when a character is received. We are going to use the second method here, following are the steps. Create an Event for a particular action like character reception, change in modem lines etc using SetCommMask function.
Ask windows to wait for the event set by SetCommMask function using WaitCommEvent and notify us when the condition happens. Call ReadFile to read the received data from the Serial port.
Functions used are. SetCommMask is used to set the events to be monitored for a communication device. Codes running on Windows 7 PC. Codes running on Windows 10 PC. Check out our next section,. Anonymous not verified. The transmission of data requires the Handshaking property to be set to one of the settings above. To allow this to work, the CTS clear to send pin 8 of the 9-way , RTS request ready to send pin 7 of the 9 way which is directly controllable from software, DTR data terminal ready pin 4 of the 9-way again this is directly controllable from software and DSR data set ready is similar to the CTS pin but is activated by other end of the connection.
Handshaking can be none which is the most common these days. The handshaking was originally used when the speeds were lower and it would cost more time to resend the data, it is used also if a large amount of data is to be sent to ensure it has been correctly received. Detailed above are the available settings from the serial port class. The diagram below shows how to connect up two 9 way D-types for full duplex communication. If the true property is replaced with false , the switch over of the voltages can be seen.
These values were measured on the PC being used to write this article using a mulitmeter set to volts mode and Pin 5 of the 9 way as ground. I found when I was learning software communications, too much time was spent explaining the theory not enough was doing.
A button called btnTest is created and the click routine is as follows this code is included in the listing and example project but commented out, uncomment to use! The RS connection has a wire from the DTR or RTS pin and makes contact with the pins shorting them , it causes the labels backgrounds to change like so:. To get this functionality, the following lines should be added below the SerialPort declaration:.
This will create the objects needed. The line below should be added to the form declaration below InitializeComponents ; :. I have found it easiest to run this program with a female socket of the end of a 9 way cable. A piece of wire can then be stroked over the pin solder buckets casing the labels to change colour from Green to Red and back , this will give some feeling that you achieving something.
It should be noted at this point the PC will try to open the default serial port which is default is Baud, No Parity, One Stop bit and No flow control, the number is decided by the lowest number serial available Com1 if fitted. All this does is connect Pin 2 of one RS port to Pin 3 of another, and the Pin 2 to Pin 3 of the other end, while this is all that is needed, a connection between the shield grounds is recommended to prevent errors.
Pins 2 and 3 are directly connected Tip : The pin spacing on a standard 9-way D type is just right to all a jumper from the back of an old CD-Rom to be used! To get the demo codes to do this, add a button to the form called PortState and add the code below:.
A very good practice to get into is to use the IsOpen property to check to see if the port can be opened.
The main use for this I have found is with USB com ports which can be added and removed at will and not always placed back in the same socket an example of this is below:.
This if will check the COM port to see if it is open, the not operator is to check if it is closed. Another useful trick is to use a try … catch as below:. This will cause the software to produce a message when a fault is found and not blow up in the user's face! Also another thing the Serial Port Class provides is the Timeout Property, to prevent the software sitting waiting in a loop, you can do the below:.
The above sets a time limit on actions to the serial port. By default, these are set to infinity but can be set. I have used the Read time out with some radio boards to check they are still in range if the command to get the serial number of board X times out X is not in range.
To receive data there are two methods, interrupt using the DataRecieved Event and polling with a timer not recommend but using a stop watch timer from the tool box with a interval property of or 1 second see below for code …. Generally, this method while it works for a single serial port that does not change quickly it works, however I have been bitten by this with a test rig someone I think I know who!!
These are both valid methods, however the DataReceived event is acted upon an interrupt basis using a delegate. To get this function to work, add the below:. This is done with use of the. Write function. It can write a byte array, a character array or subarray or a string. The reading method is ReadExisting method.
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