ZUno Module Debugging

Discussion about Z-Uno product. Visit http://z-uno.z-wave.me for more details.
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AJTozer
Posts: 7
Joined: 08 Oct 2017 18:37

ZUno Module Debugging

Post by AJTozer »

I'm debugging a really strange problem with a ZUno module project.

The board has two power supply circuits: USB and battery. The USB power supply is just a 3.3V regulator and the USB_DM and USB_DP lines connect to the module. Using this PS the board works fine. I can program the module, add it to my ZWave network and it sends data as expected.

The battery supply uses an MCP1257 to create a regulated 3.3V from the battery (actually my bench supply, right now). I built a standalone version of this supply and used it to power a ZUno board so I have _some_ confidence that it will work, but I'm not a EE and quite possibly have things screwed up.

When I run on the battery supply the board starts normally. I can even see the I2C communication start in the setup() function. But after about 80ms everything stops. My code does not seem to be running any longer and the board is drawing about 10mA. I replaced my firmware with something trivial that doesn't do any ZWave radio and just toggles a GPIO pio. Same failure. About the only thing different between the USB power and the battery power is that on battery the MCP1257 LBO* signal will be HIGH on pin 6.

I've tried putting the module into rescue mode but I don't think that it worked. If it's in rescue mode then I'd expect to be able to remove it from the ZWave network and that doesn't work.

So, is there any way to probe the module with an oscilloscope to see if it is actually in rescue mode or not? Or probe it to see what else might be happening?

From the pinout I see that pin 6 is also T0 EXT CLK. Is there any reason that pin can't be used as an digital input?

Obviously, the culprit seems to be the power supply but I can't find any sags or glitches. I desoldered the module and connected the power rail to an electronic load and the PS doesn't have any problem providing the necessary current.

Anyway, sorry for rambling. I'm running out of ideas so maybe someone can give me a clue.

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PoltoS
Posts: 5956
Joined: 26 Jan 2011 19:36

Re: ZUno Module Debugging

Post by PoltoS »

Please make sure to do Serial.end() in the setup().

We have experienced that sometimes noise on USB can leat to USB core to start waiting for USB to come up. using the Serial.end() will disable USB. Still the rescue mode will work for you to upload a new sketch if needed.

Another way to go is to solder pullup on USB_DM/DP, but this will drain power from your battery and is not a good way.

AJTozer
Posts: 7
Joined: 08 Oct 2017 18:37

Re: ZUno Module Debugging

Post by AJTozer »

Thanks for the quick reply. I need to get the module soldered back to my board and then I'll try doing Serial.end() in setup(). That sounds like a great clue.

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PoltoS
Posts: 5956
Joined: 26 Jan 2011 19:36

Re: ZUno Module Debugging

Post by PoltoS »

And make sure to use 2.17!

AJTozer
Posts: 7
Joined: 08 Oct 2017 18:37

Re: ZUno Module Debugging

Post by AJTozer »

I got my board re-assembled, updated to 2.1.7 and added a Serial.end() at the beginning of setup().

And, it works! Thank you so much for the great idea. I don't want to admit how much time I've spent trying to figure out what I did wrong with the power supply.

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