Monday, October 17, 2011

Arduino Grapher progress

I have now committed the current progress to Github - https://github.com/xiphiaz/Arduino-Debugger

Since the last post I have expanded the project from just interfacing individual sensors, to tracking the activity of all the pins on the arduino. This will allow users to have their own project code running on an arduino, and connect another Arduino running my software to the first one. The benefit of this is that the user will be able to check on their own code, to see that the digital pins are going high when expected, and that the analogue pins are receiving the expected values.

One thing I would like to add is to give the grapher the ability to draw in 3D, which would be very useful for checking on multi-axis sensors.

I initially looked in to using firmata for the sketch on the probe arduino, however I quickly realised that firmata wouldn't be suitable as it does not provide good timestamping on the messages, which is important for graphing accuracy. Also as firmata uses the MIDI protocol there is significant overhead on the size of the packets, which would limit the quantity of data crossing the serial interface, which would drop the polling frequency to an unacceptable level.

Because of the limitations of firmata I have developed my own sketch that simply has a start/stop command and the ability to turn on/off individual pin reporting. A sample io would look like the following:

>{pin_on:a0}

>{print:begin}



[123456]{a0:127}[123472]

[123476]{a0:132}[123483]

[123497]{a0:195}[123503]

The returned message is fairly lightweight, so a lot of data can be sent at high rates, and will be easily parsed by the master software.

I have also been developing a method of changing the baud rate on the fly, as when lots of data is being passed through the serial interface polling rate drops. By upping the baud rate it is possible to get a higher throughput of data, at the cost of cpu cycles on both the arduino and the host computer.

Tags: arduino microcontroller electronics arduino_grapher

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