4 replies to this topic

[mcinnes01]

Hi,

I am just looking a little further in to data logging, I building an aquarium controller and will measure multiple temperatures, ph and maybe a few other things as my project grows...

Basically I want to know if its possible and how I would go about navigating through data that I log, and logging multiple things?

Background: I am using a netduino standard and a sparkfun microSD shield and a gain span wifi module. (Not the N+)

I also want to store user variables on to the sd that can be used to reset the device if the power is disonnected.

Eventually I plan on having the data upload to an SQL database, but it will always write to the sd as a backup, then reconcile the server when the connection is restored. Perhaps keeping a week of backup on the SD, so the navigation will come in to select all records that are older that 1 week and delete them. I just about have my head around databases but I don't really understand how data is held on the sd?

This is the code I have used to write to the sd so far in testing:

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;
using SecretLabs.NETMF.IO;
using System.IO;

namespace SDCardTest
{
    public class Program
    {
        public static void Main()
        {
            StorageDevice.MountSD("SD", SPI.SPI_module.SPI1, Pins.GPIO_PIN_D8);

            using (var filestream = new FileStream(@"SD\dontpanic.txt", FileMode.Create))
            {
                StreamWriter streamWriter = new StreamWriter(filestream);
                streamWriter.WriteLine("This is a test of the SD card support on the netduino...This is only a test...");
                streamWriter.Close();
            }

            using (var filestream = new FileStream(@"SD\dontpanic.txt", FileMode.Open))
            {
                StreamReader reader = new StreamReader(filestream);
                Debug.Print(reader.ReadToEnd());
                reader.Close();
            }
            StorageDevice.Unmount("SD");    
        }
    }
}

Thanks in advance for the help, also how would I go about having this as a background process, I am totally new to multi-threading and still don't understand it much, but I guess this project is going to end up with a lot of processes occuring symultaneously. I've seen OMAR's example but could do with understanding how I could apply it to a situation like data logging while other things like readings are being taken and decisions made to turn things on and off at the same time, along with pwm lighting control and fan control etc.

Andy

[Mario Vernari]

Not sure to understand what's your actual goal. Do you mean to log the whole set of vars every specific interval? For instance, every hour? Anyway, I would use a file of each "sample" set of vars. Each file is named sequentially (e.g. Log0001.bin, Log0002.bin, etc) For the file format, I'd consider the raw-binary, the plain-text (ASCII) or the Xml. The easiest is the last, but it also requires enough resources (and CPU time) compared to the others. Hope it helps. Cheers

[mcinnes01]

Hi Mario, How is the data held using ascii or raw binary and how can I use the data in that format to query e.g. to delete data over 24hours old as a write of new data is done. Or to enquire on the largest value in a time or date range? What method would you recommend and can you provide any examples or expand on the code example above? Cheers, Andy

[georgejh]

Hi Mario,

How is the data held using ascii or raw binary and how can I use the data in that format to query e.g. to delete data over 24hours old as a write of new data is done. Or to enquire on the largest value in a time or date range?


What method would you recommend and can you provide any examples or expand on the code example above?

Cheers,

Andy

I would suggest you to use XML file(s). Have each record attributed with ID and DateTime.
You can then navigate the records with XmlReader (System.Xml) or write them with XmlWriter. To use XmlWriter you need to add reference to MFDpwsExtensions.dll from "le" (little endian") folder of .NETMF (wherever you installed it to - example: "C:\Program Files\Microsoft .NET Micro Framework\v4.1\Assemblies\le\MFDpwsExtensions.dll". Then add "using System.Ext.Xml;". Now you should have access to XmlWriter.

[mcinnes01]

cool thanks will give it a whirl and will let you know.