SD Card Reading with External Power

Hi.  I have a Very simple program that creates a file on an SD card at boot up.  If the File exists, it lights the LED and deletes the file (so the next boot up the LED is off).

 

This works perfectly while plugged into my computer via USB -- every other reboot the LED is on.  When the ND is being powered by an external power supply it does not work -- EVERY reboot the LED is on.

 

I have an ND+1 with 4.2 and a 2GB SD Card formatted to FAT32.

 

Any ideas?

Imports Microsoft.SPOTImports Microsoft.SPOT.HardwareImports SecretLabs.NETMF.HardwareImports SecretLabs.NETMF.Hardware.NetduinoPlusModule Module1    Public _onBoardLED As OutputPort    Sub Main()        _onBoardLED = New OutputPort(Pins.ONBOARD_LED, False)        If System.IO.File.Exists("SDRebootMe.txt") Then            Do Until System.IO.File.Exists("SDRebootMe.txt") = False                System.IO.File.Delete("SDRebootMe.txt")            Loop            _onBoardLED.Write(True)                   Else            Do Until System.IO.File.Exists("SDRebootMe.txt") = True                Dim file As New System.IO.FileStream("SDRebootMe.txt", System.IO.FileMode.Create)                Dim SR As New System.IO.StreamWriter(file)                SR.WriteLine("FooBar")                SR.Flush()                SR.Close()                file.Close()            Loop            _onBoardLED.Write(False)        End If    End SubEnd Module

Thank you!

Terry

I suggest that you get out your voltmeter and see what voltage the Netduino is seeing from the external supply.

Hi jrlyman3.  Very good advise.  I just checked and the board is getting 9.41V.  Right in the middle of the expected range.

 

 

Hi seascan, How noisy is your power supply? Do you have another one you can try? Also...if you power the board up via a USB wall adapter...do you get the same results? Chris