Send Raw or hex data out the serial port using bonescript

John Mladenik

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Nov 19, 2014, 6:26:23 PM11/19/14

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I need to be able to send raw data out of the serial port using Bonescript command b.serialWrite. I set up an HTML Bonescript to send data and then looked on the logic analyzer to see what bit pattern is sent out. The pattern is always the ASCII value of the character whether the variable is a text or number.

Does anyone know how to pass to b.serialWrite a value so that the UART outputs that value?

so I want to have

var port = '/dev/ttyO2'; // set UART port

var data = 0x55 ;

b.serialWrite(port, data );

and for the bit pattern coming out of the UART to be 01010101

I tried using String.fromCharCode(data); but this only works for values up to 127 (0x7F) since that is all ASCII goes to. This must not support extended ASCII?

here is my html/javascript to test this functionality

<html>

<body>

Uart Byte:<br>

</body>

<head>

function uartWr() {

var b = require('bonescript');

var port = '/dev/ttyO2'; // set UART port

var data = document.getElementById('value').value;

// set baud rate and buffer size

var options = {

baudrate: 9600

};

b.serialWrite(port, data );

}

</script>

</head>

</html>

George Lu

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Nov 19, 2014, 6:44:26 PM11/19/14

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I recall BoneScript uses https://github.com/voodootikigod/node-serialport for serial port interface.

You should be able to send raw binary with b.serialWrite(port, [0x55]);

Data should be a buffer (http://nodejs.org/api/buffer.html).

John Mladenik

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Nov 19, 2014, 7:03:12 PM11/19/14

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Yes that worked thanks.

John Mladenik

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Nov 22, 2014, 10:49:10 PM11/22/14

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So it worked but once I let the board sit not being powered overnight it stopped working. Do you or anyone know how to get the UART2 working and stay working once powered down and then turned back on?

George Lu

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Nov 24, 2014, 10:43:55 AM11/24/14

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On Sat, Nov 22, 2014 at 7:49 PM, John Mladenik <john...@sbcglobal.net> wrote:

So it worked but once I let the board sit not being powered overnight it stopped working. Do you or anyone know how to get the UART2 working and stay working once powered down and then turned back on?

Once power cycled, you would need to start up the program again so that the serial port could be properly opened for writing. I would have the bonescript code in, say, /home/debian/doSerial.js, and run that automatically on every reboot. There are a number of ways to do this. One quick way is try to add a line in /etc/crontab to run this command on @reboot:

@reboot root cd /home/debian && NODE_PATH=/usr/local/lib/node_modules && export NODE_PATH && doSerial.js

Assuming you are using debian image, /dev/ttyO1 and /dev/ttyO2 have "rw-rw---" as their permission. So you either need to run it as root or add your desired user to the dialout group to be able to write to these serial interfaces.

If doSerial.js crashes for any reason, you could use a process monitor to restart it. Supervisord, forever, pm2, are some options to explore.

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John Mladenik

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Nov 25, 2014, 1:46:10 PM11/25/14

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My UART2 app worked the whole time, I had the logic analyzer probes on the wrong pins and thought it was not working. I found this once I tried a 2nd BBB and it worked right out of the box. I then went back and realized the probes were on the wrong pins.

thanks for all the help.

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