Serial buffer processing

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Asked 3 years, 8 months ago. Active 3 years, 8 months ago. Viewed times. Improve this question. However, before you go into this part of the source code, you need to understand readStringUntil as in when to use it and how to use it with the available functions.

A challenge for you, if you are interested, is to use a Thread to simulate incoming serial data. How does Serial. Processing Electronics Arduino, etc. For example, in the code below: import processing. I see there are serial methods of controlling how the buffer is read, thanks for the resources.

If the message has exceeded the max length in the protocol, then we need to stop reading in more bytes and output the message, or do whatever we want with the message for that matter. So now we've got a strategy for reading in a message from the serial receive buffer. In part two, we'll be implementing all of this into code.

I look forward to seeing you then. Maybe you're using the Arduino serial monitor window and sending in data or maybe you've got a program running on your Raspberry Pi that sending data via serial to your Arduino board. This lesson is a continuation of part one.

In this lesson, you will learn the code to use Serial. All right, now I hope you're doing fantastic. Again, this is part two of Using Serial. So if you haven't seen part one yet you're really gonna wanna watch that. In part one, we talked about the big picture of serial communication. We talked about the serial receive buffer, Serial. Then we developed a protocol and a strategy for reading in the data from the serial port. In this lesson what we're gonna do is implement that strategy in Arduino code.

And as a bonus, you'll learn how to convert the serial data from a string to an integer. Alright, let's get started.

And this is essentially the algorithm that we talked about in the last lesson. I'm just gonna run through the things that we need to do. So one we wanna create a character array to store incoming bytes.

We wanna check to see if there's anything in the serial received buffer to be read. While there is something to be read then we wanna read in the byte to a temporary variable.

We wanna check to see if what we read is part of our message, or if it's a terminating character. If it is a part of our message, then we'll save it to a character array. If it's a terminating character then we can output the message or do something with it and prepare for the next message.

If the message is exceeded the max length in the protocol then we need to stop reading in any more bytes and just output the message or do something with it. Now we're about to jump in to some really technical stuff. If you're interested in learning how to program and create electronic prototypes, I definitely recommend checking out Programming Electronics Academy.

We've got in-depth, concise, video training that walks you through all this kind of stuff so that you can go out and start building your own projects. All right, now on that.

So let's go ahead and start with a bare minimum Arduino program with a setup and loop. We'll also add Serial. Notice that in Serial. This is called the baud rate. It sets the speed of the serial communication and it represents bytes per second. So this would be 9, bytes per second going between the two devices.

Now, both devices must have the same baud rate selected in order for serial communication to work. If you're using the Arduino IDE serial monitor window to send the data then the baud rate can be set using the dropdown menu. And there's a bunch of common baud rates that you can use but we're not gonna get too much into that right now.

You just need to make sure that the sending and receiving devices both have the same baud rate set. Okay, so we've got this base program set up now let's tackle the first step of our algorithm. We need to create a character array to hold the incoming message and a position variable to help us move through each element in the array.

We'll also create a constant to hold the max length of our message and use that to initialize our character array. Okay, so let me do that. This is an arbitrary length. This is something that you're gonna choose. Then we created a character array named message. In array is a data type that can hold multiple elements. Arrays can only hold one type of element. So we're making a character array. This is going to hold characters.

So each of the characters that we read from the serial received buffer is gonna be going into this character array. Finally, we've got this message position variable. This variable is gonna allow us to choose where in the array to putt incoming bytes. All right, so we've got that done, I'll go ahead and mark that off the list of to do's up here.

Now, what we need to do is check to see if any bytes are available in the serial received buffer. And while there are bytes there, we need to read the bytes in and save them to a temporary variable. We can use a while loop Serial.

So if you'll recall from the previous lesson Serial. So if there's any data in serial received buffer this value, this returned value will be greater than zero.

So what we're saying is that while there's still data inside the serial received buffer this code is gonna run over and over and over. And then what we'll do inside this while loop is read out those bytes one at a time using the Serial. All right, so we've got that done.

I'm gonna go ahead and check that off our list. Check to see if there's anything in the serial receive buffer. We do that with Serial. And then while there is something to be read, we read in the byte to a temporary variable. So we just did that. So now we need to check to see if what we read is part of our message, or if it's a terminating character. What we could use is an if else statement for that.

If it's not a terminating character will do one thing and if it is a terminating character will do something else. So let's do that. So what we're trying to achieve here is we wanna make sure that we haven't gotten to the end of our message. If we're reading in a message and there's another message after it, we don't wanna just like start reading into the other message.

We need to know where the first message ends. And that's why we have these terminating characters. So what we're doing is we're reading in that character and we need to check, Hey, is this part of our message or is this a terminating character and lets us know it's the end of a message. So what we do is we check if it's not a new line. So this little thing is a new line and we say not new line. So we're checking, Hey, is this byte we just got? We wanna make sure it's not a new line. If it's not a new line, that means it's part of our message and we'll do something.

If it is the new line, then what that means is that we have received a full message and then we're gonna wanna do something else.

Okay, so we're doing our check for the terminating character. Let's go ahead and knock that off our list up here. All right, getting stuff done. Okay, so if it's part of our message then we wanna save it to the character array. And then we'll also need to increment our position in the character array for the next byte.

So what we're doing here is we have our character array. Again, this is gonna be the place where we store the incoming bytes. The value that goes inside these brackets tells us where we are referencing. So this message position right now, it's set to zero. That's what we initialized it at, is zero. So what that means in the first position of this character array, we're going to putt in byte.

So if we had the message, if we just sent the message like sub, then the S would be, you know what invite is. And the S would go in the first position in that array.

And that's because arrays are zero indexed. Now, if all this sounds like Greek to you, again check out Programming Electronics Academy. We talk about all this kind of stuff. I know you might feel like man you're glossing over so much stuff.

Well, there's just a lot to learn, but it's definitely doable. Anyway, all right I digress. Okay, so we save in this incoming variable to our array. And then the next thing we do is we increment our position variable. So we say message position plus, plus. We're adding one to this variable.

So before it was zero, when we started out. After this line of code, it's gonna be one. So what that means is the next time through here when we pull in the next byte from the buffer we're gonna save it in the next position. So you can see we're kind of reassembling the message.