Embedded DataLogger - Uploading data to App Dev

[jay_dee]

Hi,
A customer go me thinking So just thought I would throw some ideas about.
( Honestly I really dont need an extra embedded project but...)

Could you get a PIC to save a continuous sensor reading to a removable SD card in an embedded project, then,
at a later date retieve/read the data into a App Dev project.
Then use App Dev to display / scroll the data.
I'm thinking about a single sensor, 16bit Value, 20Hz for 1 hour. that would be 144 kByte of data.

Obvious issues I can see,
how to read data from the SD Card
Could I get App Dev to handle the large number of data bytes, 144K
Graphing the data
Scrolling and zooming into a graph of data sounds tricky.

Currently just an idea and intertested if it seems fairly do-able.
thanks. J.

[Steve-Matrix]

That's an interesting project and perfect for PC Developer.

Reading data can done in various ways. For example, direct from an SD card that has been removed from your hardware and inserted into the PC, or via comms to the embedded app, in which case the embedded app reads the data from the SD card (or memory) and sends the values via a serial link.

Graphing the data should be ok, but that many points might take a while to fully display. There are some tricks like temporarily setting the X-axis to small range (e.g. between 9999 and 10000) and this allows the chart to be added to without redrawing each added point. Once all the data has been added to the chart, change the X-axis back to the full amount.

Scrolling and zooming can be handled in a similar way. Add controls to the chart that allow the X and Y Start/End values to be set. This will allow you to zoom in and out.

I've attached a basic app that plots data and has controls to set the max/min x values on the chart. Hopefully it makes sense. One thing to note is to redraw the chart you have to click on it.

[jay_dee]

Thanks Steve, that is a great kick start idea for a graphing tool. I should finish the other project first but this looks interesting! J.