AVR 128da curiosity nano power supply issue

Go To Last Post
9 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The Micro Chip Curiosity Nano board for the AVR128da48 is a nice dev board.  It comes with a built in programmer that works with their MPLAB IDE.  However, the  board does have an issue with the built in power supply.  Normally, the board is powered off of the USB port.  The on board voltage regulator can be set to anything from 1.8v to 5.5 volts under control of the IDE, and the board will 'remember' this voltage setting the next time it is plugged in.  Since the built in debugger is built on a SAM chip, it runs off of a separate 3.3 volt regulator, and a level converter is used to interconnect the processor with the debugger.  The debugger also includes a USB to Serial converter, and this provides a USB Serial (ACM0 device) on the USART 1 device (port pins PC0 and PC1).  

The one fly in this ointment, is that the CPU end of the level shifter is powered by the on board target regulator.  While you can disable the target regulator by grounding one pin of the Nano, and then provide external target power, with the internal regulator turned off the level converter doesn't work!  I wondered why my application would not work with the serial port when externally powered, this is the reason!

The end result is that you can't easily built a project around the Nano, and externally power it, not if you want to use the USB serial port anyway!  There may be a work around here, but I fear it will involve micro surgery to attach a bodge wire.  Anyone else run into this?

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Did you see this:

Programming, debugging, and data streaming is still possible with an external power supply – the debugger and signal level shifters will be powered from the USB cable. Both regulators, the debugger and the level shifters, are powered down when the USB cable is removed.

 

http://ww1.microchip.com/downloads/en/DeviceDoc/AVR128DA48-Curiosity-Nano-UG-DS50002971A.pdf

 

What ext supply are you using?   Of course gnd needs connected.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I was using an external 5v supply.  I did have the gnd connected.  The schematic block diagram in the user manual shows the level converter being powered on the other side of the power supply strap from the VTG pin.  External power is applied to the VTG pin.  Well, it looks like it SHOULD work, but I don't think it was working.  I'll recheck my connections, but just grounding the VOFF pin and putting 5v on the VTG pin didn't work last time, removing both of those connections and it does work.  USB was always connected.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

 The schematic block diagram in the user manual shows 

Forget about that, you can look at the actual schematic they usually provide---may be more useful, since it is the actual PCB.  Print it out and label your hookup & you can trace it out

 

http://ww1.microchip.com/downloads/en/DeviceDoc/AVR128DA48_Curiosity_Nano_Schematics.pdf

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I tried it again and got it working on the external power supply.  It seems to be an issue with the order of things.  The switch that shuts down the internal target regulator is controlled by the debugger, and the voff signal goes to the debugger chip.  So you must have the voff grounded, and then plug in the USB BEFORE applying external power to VTG.  If I do it that way, it works.

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

So you must:

 

1) Wire up the Voff connection pin

2) Plug board into USB/PC     ..(this must be done before step 3)

3) Turn on the board external power supply.

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Which debugger firmware version are you running?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

 

So you must:

 

1) Wire up the Voff connection pin

2) Plug board into USB/PC     ..(this must be done before step 3)

3) Turn on the board external power supply.

 

 

That's what worked for me anyway.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

mraardvark wrote:
Which debugger firmware version are you running?

 

MPLAB IDE 5.40 on Linux.  I don't know what debugger firmware is installed in the EDBUG on the Curiosity Nano.