Matrix Not Responsive - Hardware Issue?


#1

Questions:

  • Is there a detailed schematic I can use to troubleshoot/repair my Matrix?
  • Does Matrix Labs do repairs or swap outs?

My Matrix Creator has worked well for a few months. Yesterday, I thought my battery went dead.

However, I believe it appeared as such due to a shorted component on the board downstream of the Matrix boards 3.3V regulator located at the top left as pictured below.

The bummer is that I am in the middle of an Element14 Presents video production showcasing the Matrix Creator when this happened. :anguished:

I have been using it to drive an H-Bridge (L293D) with GPIO 0,2,4,6 and drive a servo with GPIO 1. I had not put any current limiting resistors in the Matrix GPIO and the H-Bridge as all tutorials omit them. The servo is powered by a 5V pin of the Matrix.

When I hook up a power source voltage/amp reader, this is what I see:

  • My wall wart for this test is 5V @ 2.4A. I used two separate Raspberry Pi’s and got the same results.
  • 5V supply is pulled lower to 4.4V when Matrix is installed
  • 0.38A of just the Pi is raised to 2.8A when Matrix is installed. This is probably the max the wall wart can deliver and, to me, indicates a component is shorted.
  • Pi won’t boot due to this under voltage condition.
  • Matrix Onboard 3.3V regulator gets hot quickly.
  • Matrix Onboard 3.3V regulator shows 2.86V where it should be 5V. My assessment is that there is a down stream short in the circuit that is pulling down the voltage.
  • Matrix Onboard 3.3V regulator shows 2.11V where it should be 3.3V.
  • Matrix Onboard 3.3V regulator shows no resistance to ground on its Vout (3.3V) pin. This to me tells me there is a short to ground downstream.
  • Removed the Matrix Onboard Regutator and Voltage and Amps are fine with Matrix installed. This is most likely because I disabled the Matrix downstream circuitry by doing this.
  • With the regulator removed, I still see no resistance to ground between the regulators 3.3V pad and the ground pad.
  • When I substitute a battery source that can deliver higher amps, the Pi does boot, but the Matrix just flickers its front Blue LED and does not respond to code.

Thanks,
Sean


#2

HI @sjmill01, we will email you regarding this to provide any info you need to fix it :slight_smile: .

-Yoel


#3

Thanks so much.

I believe I found the root cause of the failure. My Hbridge circuit had a short between the GPIO 2 and GPIO 4 (pins 3 and 5) of the Creator board. This would be a problem when pulling 2 low and 4 high or 4 low and 2 high.

The short was just a little bit of solder that needed scraped away between the corresponding pads of my Hbridge circuit. I found it by connecting the board directly to the Pi - although it didn’t blow anything.

Please pass this scenario to your engineers to see what I could do to salvage the Creator.

Thanks,
Sean


#4

Hi @sjmill01,

Sad to hear this, it looks like, even after removing the 3.3v regulator, you still have something shorting 3.3v pad to ground downstream, correct?
From what you said when you talk about the GPIO2 and GPIO4, I am assuming they are from the external GPIO connector that MATRIX Creator has and no from the Raspberry Pi connector.

One question:
Have you noticed any other component getting hot when you had the 3.3V or after you removed it?

In another topic, it is worth to say that pretty much everything on the board is connected to that 3.3V net, just LEDs ring uses the 5V. In the 3.3V net, sensors could be easily isolated from power, but the FPGA is really difficult to isolate because of many pins connected to 3.3V. Also, because the shorted GPIO2 and GPIO2 pins are directly wired to the FPGA the most likely component causing this is the FPGA itself. Did you notice if the FPGA also got hot?

-Yoel