In this project, I plan to use an Arduino to read data from a sensor and store it on an SD card. The system should work completely autonomously, without being connected to a computer. The Arduino will continuously collect sensor data and save it to a file on the SD card.
I know that i would be easier to simply collect the data and later transform it to a Diagram but I want to use it as a project to learn more about that topic
Since I am not very familiar with this topic, I am open to alternative ideas I already thought about BMP but dont know if it suits my demands
Because SD card operations are all blocking, you will not be able to do anything continuously. That is why when something needs to be collected continuously, it is sent to a connected PC for storage.
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What do you mean by "diagram"? Do you mean a chart, or graph, representing the data?
Where will this chart be displayed? An SD card cannot display a chart. What will read the SD card and display the chart?
An alternative to BMP could be Scalable Vector Graphics (SVG) as part of an HTML file. Using this format, the Arduino will not need to deal with individual pixels, but instead create the chart from lines, text and other elements.
I am using an Arduino Uno connected to a DHT22 sensor and an SD card shield. The system records new temperature data approximately every two seconds. I do not want to use an LCD or any live display.
The setup will be installed in a remote-controlled airplane to collect environmental data during flight. My goal is to avoid manually converting the recorded values into a graph later. Instead, I would like the Arduino itself to generate the coordinate system and continuously add new data points to it.
Ideally, the graph should look like this:
y Temperature (°C)
|
|
|
|
0----------------------------------------- x Time (s)
Each marker (such as "|" or ".") would represent a defined unit of temperature or time.
Is it possible to create and continuously update such a coordinate system directly on the SD card, so that new points are permanently added and the finished graph is immediately visible when opening the file on a computer?
So you want to use ASCII symbols to draw the graph? You mentioned BMP file before, so I was imagining something more sophisticated.
Yes, this could be done with ASCII symbols. You could rotate the graph by 90 degrees so that the temperature axis is horizontal and the time axis is vertical. Then each time the Arduino takes a temperature reading, it can add an extra point to the graph.
How many data points do you want to display in the graph?
A separate graph could be drawn for perhaps each 15 min period, and saved as separate .html files which can be opened and displayed on a pc directly from the SD card.
That looks like that what i have been looking for, could you perhaps give some intel on how you did that? I thougt about collecting data for roughly 5 minutes with a three second interval so a total of 100 datapoint.
My charts like the one above are created by a PHP script which runs on a server PC which uses a MySQL database to store the data. The "Arduino" sends the data to the server every 15 mins.
But there's no reason why Arduino code can't draw similar SVG charts directly, except perhaps the very limited memory that some Arduino models have. What model of Arduino are you planning to use?
