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How to add USB pen drive data logging

If you want to add USB pen drive data logging to your system the Vinculum VDIP1 USB host controller works really well.

There are a couple of places you can get the board, farnell stock them for £13.94.

There are some good guides on using the board with an Arduino. I found these two most useful. I recommend reading these to get an idea of how it all works. I've added a couple of things to increase the functionality and get rid of write errors, which are documented below.

Guide 1 - Writing data to Usb Memory Stick – by Nick on the Arduino playground.

Guide 2 – Usb Storage and Arduino – by Sven Steinbauer

Additions

Wait for 'ok' response

The Vinculum board is controlled using DOS commands. Every time you send a command, if the command is executed successfully, the board sends a “D:\> ” response that indicates it's ready for the next command. Commands sent faster than the board can execute them, and not waiting for the “D:\> ”response resulted in stored data errors and sometimes a crash.

To solve this, the Arduino sketch listens for a response from the board after it sends each command, if it receives “D:\> ” then it can send the next command. If it receives “No disk” it stops trying to write to a non existent disk and waits until a disk is inserted and the start write button is pressed.

Start/stop write button and led indicator

Just a simple start/stop write button. To start writing hold the button down for 2 seconds. The LED illuminates to indicate writing. To stop writing, hold it down again for 2s, and the led turns off. If the Arduino receives a 'no disk' response. The LED is automatically turned off.

Hardware

Vinculum VDIP1 wiring diagram:

Start/stop push button and LED indicator circuit diagram:

Layout suggestions

A piece of stripboard to mount the Vinculum VDIP1.

Start/stop push button and LED indicator

Installation example in the home energy monitor main unit

Arduino software:

The Arduino sketch works with the board independently of any other energy monitor hardware and code. It writes the values set in the variable declaration, to the board as an example.

1. Download the Data logger Arduino sketch
2. Compile and upload the Arduino sketch. For a guide on compiling and uploading the sketch, have a look here.
3. Check your Arduino serial monitor for write status. Once you have pressed the button you should see the following output if it's working correctly:

Started
O D:\>
W D:\>
C D:\>
O D:\>
W D:\>
C D:\> 

If you see the correct responses (as above), press the button again to stop writing. You should see "stopped" on the serial monitor. Check the USB pen to verify the data is there.