It was never designed for doing things like speech synthesis or music playback, and driver attempts to use it for those purposes sound awful. Still, it is something neat to experiment with and a legacy computer part that is surprisingly still used on many current computers..
I'm going to go back to the serial terminal program for a bit and this time redo the application by using an interrupt service routine. There are a few other concepts I'd like to introduce as well so I'll try to put them in with this example program.
From the user perspective, I would like to add the ability to change the terminal characteristics from the command line and allow an "end-user" the ability to change things like the baud rate, stop bits, and parity checking, and allow these to be variables instead of hard-coded constants. I'll explain each section and then put it all together when we are through. This isn't that much different from the polling method that we used earlier, but keep in mind that by placing the checking inside an ISR that the CPU is only doing the check when there is a piece of data available.
Why even check the LSR to see if there is a data byte available? We will go over that in detail in a later section, but for now this is good programming practice as well, to confirm that the data is in there. We could even put the keyboard polling into an ISR as well, but we are going to keep things very simple for now.
There is one minor problem with the way we have written this ISR. Instead, all we are going to do is simply disable the FIFO completely. Clearing the FIFOs look like this:. We will be using the FIFOs in the next section, so this is more a brief introduction to this register so far. Now we need to.
There isn't the need to do all of the potential instructions for the PIC, but we do need to enable and disable the interrupts that are used by the UART. When we do the "cleanup" when the program finishes, we also need to disable this IRQ as well with this line of software:.
That will be demonstrated a little bit later. This signals to the PIC that it can clear this interrupt signal and process lower-priority interrupts. If you fail to clear the PIC, the interrupt signal will remain and none of the other interrupts that are "lower priority" can be processed by the CPU. This is perhaps the most non-obvious little mistake you can make when trying to get the UART interrupt. Because of the way the circuitry on the motherboards of most computers is designed, you usually have to turn on the Auxiliary Output 2 signal in order for interrupts to "connect" to the CPU.
In addition, here we are going to turn on the RTS and DTS signals on the serial data cable to make sure the equipment is going to transmit. We will cover software and hardware flow control in a later section. We are still not home free yet. We still need to enable interrupts on the UART itself. This is a very simple line to add here:. At this point you start to grasp how complex serial data programming can get.
We are not finished yet, but if you have made it this far you hopefully understand each part of the program listed above. There are a number of different ways that you can "scan" the parameters that start the program. For example, if you start a simple terminal program in DOS, you can use this command to begin:.
Obviously there should not be a need to have the end-user recompile the software if they want to change something simple like the baud rate. What we are trying to accomplish here is to grab those other items that were used to start the program. In Turbo Pascal, there is function that returns a string. These are passed to the program through strings.
A quick sample program on how to extract these parameters can be found here:. One interesting "parameter" is parameter number 0, which is the name of the program that is processing the commands. We will not be using this parameter, but it is something useful in many other programming situations.
For the sake of simplicity, we are going to require that either all of the parameters are going to be in that format of baud rate, bit size, stop bits, parity; or there will be no parameters at all. This example is going to be mainly to demonstrate how to use variables to change the settings of the UART by the software user rather than the programmer. Since the added sections are self-explanatory, I'm just going to give you the complete program.
There will be some string manipulation going on here that is beyond the scope of this book, but that is going to be used only for parsing the commands. To keep the user interface simple, we are using the command line arguments alone for changing the UART parameters. We could build a fancy interface to allow these settings to be changed while the program is running, but that is an exercise that is left to the reader.
Press any key on the keyboard to quit. Press "Esc" to quit. Computer Math and Games in Pascal. Lazarus Handbook. Advanced search. Member Posts: sector name toys respect to spectre. Member Posts: Im using synaser from Synapse. Thaddy Hero Member Posts: Quote from: bigeno on March 14, , am.
The average programmer productivity is hours per day. Peak performance 72 hours for short bursts. MTBF is 1 second or less. Quote from: zanden30 hetnet. Quote from: Thaddy on March 14, , am. Create ;. Viewed 2k times. One ; But I couldn't understand how to convert the rest of the pascal procedures. IsOpen port. Open ; port. ReadByte ; port. WriteLine Math. Eliyah Eliyah 3 3 silver badges 14 14 bronze badges. Add a comment. Active Oldest Votes. RxWait waits for the receiver ready status bit.
Hans Passant Hans Passant k gold badges silver badges bronze badges. I see. When you said 'just add the byte you send to a checksum variable', is this correct? It is correct. Presumably you'll need to send that checksum value as the last byte of a message.
And set it back to 0 before you start sending the next message. That's usually the way it works anyway. Thanks for the reply. At first I was trying to compile the pascal code using FreePascal but it doesn't support the port array and the go32 unit for win If I could get a way to manipulate the ports from FreePascal, in any way possible, I will then compile it to a dll file and then export it to use it from C.
NET using platform invoke. Is there a way I could achieve this? And What ever you give to Parallel port as voltages can be read from these registers with some restrictions. Just like this ,we can programmatically turn on and off any of the data lines and Control lines. Where these registers are? We have to find these addresses to work with parallel port.
So once we have the base address , we can calculate the address of each registers in this manner. Programming Concepts Almost all programming languages allow programmers to access parallel port using some library functions. And the examples provided here in this tutorial is written in Pascal. First, you should make your program in Turbo pascal for DOS. Paralel Monitor. You are commenting using your WordPress.
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