There are a couple of ways to go about it. You could read a byte (that's what Serial.read returns; not an int), and make some decision based on that character, then read again.
Active3 years, 9 months ago
I'm trying to do some fairly simple serial communication and have things partially working, but am pretty confused about a couple results I'm getting.
For a little background, I'm using an Arduino Mega 2560 to try to communicate with a Dynamixel servo (MX-64) over TTL (half-duplex, asynchronous) with Tx1 and Rx1. Basically I construct some byte arrays as instructions, send them over to the servo (with
Serial1.write() ), and then read back a reply. I've actually gotten it to work pretty well if I use Serial1.readBytes() , specifying the length of the buffer (number of bytes I'm expecting). I'm also reading back what I originally sent (first) as well as the response (second), since I have Tx1 and Rx1 tied together (required in my setup because this servo only has one data wire).
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Arduino Serial Read Multiple Bytes
However I don't understand the difference between
Serial.readBytes() and Serial.read() . If I do Serial.read() just prior to Serial.readBytes() , it comes back with -1, meaning no bytes to read.. but then Serial.readBytes() gives me the byte stream I was expecting from the buffer! What's going on here?
Similarly,
Serial.available() seems sort of broken in that it tells me there are no bytes to read (returns 0), but then I can read the bytes I'm expecting with Serial.readBytes() . Additionally, I can do Serial.readBytes() after there's nothing left (or rather, there shouldn't be any bytes left..) and it will give me some bytes, but they're total garbage.
I think maybe there's something I don't understand about the way the serial buffer works, but can't find a good resource on it and the Arduino reference pages are kind of useless. Any clues about the difference in how these operate would be much appreciated!
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thkempthkemp
1 Answer
readBytes is blocking until the determined length has been read, or it times out (see Serial.setTimeout()). Where read grabs what has come, if it has come in. Hence available is used to query if it has.
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Note that it takes time for a message to go out and to receive either the echo or response. So simply checking the RX buffer immediately after sending something, is expected to be empty for some time. That is where readBytes sites and waits. And I bet the default setTimeout of 1s is sufficient, to get the response.
This is why you see the Serial.read() inside a while or if Serial.available. Hence I typically employ something like the following: Which emulates readBytes (for the most part).
Above code was quickly written and untested. But gets the idea across.
mpflagampflaga
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Active3 years, 1 month ago
I have this code below where I got from this forum that I followed through. It did not work for me but they claim that the code is fine. I already tried several string comparison methods such as dsolimano
string.equals(string) and the standard operator, still with no luck.
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Yakob UbaidiYakob Ubaidi
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5 Answers
I am able to solve last night problem by simply adding
readString.trim(); before string comparison. This is because there will be newline character where id did not print anything in the arduino console.
I place the function as in my code below:
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andrewsi
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AnimAnim
I see you try to create some like command line interpreter for test;
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You can use Serial command line interpreter for Arduino or just see code, how it's work.
This is not answer, but some help =)
This is the correct driver for the serial adapter, and it includes drivers for Windows 7 x64. ManufacturerSupported OSWindows 10, Windows 10 (64 bit), Windows 8.1, Windows 8.1 (64 bit), Windows 8, Windows 8 (64 bit), Windows 7, Windows 7 (64 bit), Windows 2008, Windows 2008 (64 bit), Windows Vista, Windows Vista (64 bit), Windows 2003, Windows 2003 (64 bit), Windows XP, Windows XP (64 bit), Windows 2000, Windows ME, Windows 98SE, Windows 98File NameSize258.5 KBLicenseFreewareDownloads13,266Uploaded ByJacobGRocks (DG Member) on 7/24/2016Uploader NotesThis came from the driver CD that came with a cheap CH341 based USB to Serial adapter that had numerous other drivers on the CD as well. Ch340 driver download. It also seems to have drivers for Windows 98, 2000, XP, 2003, Vista, and Server 2008 as well.Driver Package.
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Arduino Serial Read Example
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solved your code is right you just have to set arduino terminal on 'no line ending' you also forgot to write this Serial.println('switching off');
and thanks for sharing your code i am also using your code thanks!!
Arduino Serial Input String
tandeltandel
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