sendString sending random characters

[jacobrosenthal]

Protocol 2.3

Using unmodified echostring example

I send "hi" to it from my host implementation, the actual bits that get sent in hex are
f0716800 6900f7

its supposed to echo back, and I get back f0716800 69000200f7

an extra 20, a space?

Sometimes a lot more characters

hi«xºœ�Ⱥ=iΩy◊Á<⁄�“w Pü˘�∂˚9‰yn+qÍΩ„<Ä~Sf¨V˚

This is the echostring write

void stringCallback(char *myString)
{
Firmata.sendString(mystring");
}

If I modify callback to send "hi" instead of the string it received
void stringCallback(char *myString)
{
Firmata.sendString("hi");
}

it sends correct data
f0716800 6900f7

If I alter the callback to print the size and bytes of the string it received
Serial.println(sizeof(myString));
for( int i = 0; i<sizeof(myString); i++)
{
Serial.print(*myString+i,HEX);
}

I get 2 characters, h and i in hex
2
6869

so sendString when sent a string is happy, but when sent a character is doing something odd

There it is:

sendSysex(command, strlen(string), (byte *)string);

Should be sizeof, which jives with working with strings, but not with character buffers like in the echo example.

Patch incoming

[jacobrosenthal]

Heh, hold on. My solution is garbage too. Working on it now

[jacobrosenthal]

Which means this is the same issues as #72 and thus #50
I glanced in there and saw talk of buffer overflow stuff and ignored it. Nevermind!

[soundanalogous]

Try the dev branch. There were actually 2 issues here. One that the strings were not null terminated when using a client library written in a language that does not null-terminate strings. The other issue was that memory for strings was never deallocated so you'd run out of memory quickly. I need to merge dev into master soon. Was waiting for some people to test a few open pull requests first (since the changes in dev require a minor version update... Firmata 2.4.0).

[hansamann]

Hi @soundanalogous - is the sendString issue solved now - I h just tried firmata / fresh mpm install and could not make it work:

var firmata = require('firmata');
var board = new firmata.Board('/dev/tty.usbmodemfd121',function(){
console.log("READY.");
setTimeout(function() {
board.sendString("Hello");
}, 1000);
});

board.on("string", function(data) {
console.log(data);
});

Thx!
Sven

[soundanalogous]

Did you load the echoString firmware Firmata example to your board? The above code should work as long as you are using echoString. However you'll run out of SRAM on the board after a few iterations (this is the bug that's fixed in the dev branch).

[hansamann]

Strange, I am using the EchoString Example from the Arduino Example / Firmata folder. Maybe there is an issue with the node code that I wrote... could you an example that simply connects to arduino and then starts the echo with sending a String?

The board I tried this with is an Arduino Leonardo, I'm on a Mac... Thx!

[hansamann]

OK, sorry for the confusion. Are you saying that the ARduino Firmata lib had an issue with receiving / sending the strings? The IDE version is 1.0.5 for me - ist that fine or should I swap the Firmata Arduino lib in this case.

For the PC part, I chose the node firmata library. Just by chance - have you used it and do you know if it is compatible with calling string functions?

Thx
Sven

[soundanalogous]

The Arduino Firmata library allocates memory each time a string is received but never deallocates this memory and therefore after sending a number of strings you'll crash the application due to running out of RAM on the Arduino. However the code you referenced should still run for a few iterations. It also appears that node firmata implements sending and receiving firmata strings so that should work as well.

Try replacing the default Arduino Firmata library with the contents of the dev branch in the Firmata repo.

Also, do you have a board other than an Arduino Leonardo that you can try? The Leonardo can sometimes be problematic with Firmata due to the way it handles serial data. There is a fix I need to add to Firmata at some point to resolve this.

[hansamann]

So I opened the Arduino.app (Mac) and replaced teh Firmata library now. Is there way I can tell it is really using the dev lib?

Unfortunately no change on the node.js side. It does nothing, then floods with "Ready." Messages (my output after it is connected) when I hit reset on the arduino. BTW the node lib we talk about is https://github.com/jgautier/firmata, right? There is a second one, arduino-firmata, but I cannot see any higher-level sendString methods.

[hansamann]

Tried with an UNO - no luck. When I start my node program, it does nothing, e.g. no "Ready." shows that it is connected.

[soundanalogous]

Clone Breakout, and checkout the dev branch. Start Breakout Server (either the Java GUI app or the headless node.js app). Then open this file in your web browser: https://github.com/soundanalogous/Breakout/blob/dev/custom_examples/echo_string.html.

Let me know if that works. That will help isolate whether this is a node firmata or Arduino Firmata issue.