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Forum Index : Microcontroller and PC projects : CMM2 - Maximite2 Kit v3.0 PCB build notes
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Womble Senior Member  Joined: 09/07/2020 Location: United KingdomPosts: 267 |
YaY  Fixed ItMany thanks Guys for all your help. Following on from advice from Phil (WW) I went over my soldering, and reflowed all the joints and cleaned up any excess solder using desolder braid where I had been a little enthusiastic. This had the benefit of ensuring there were no dry joints causing my problems. However Rob hit the nail on the head. I had been using the newest and most heavy duty USB A-B cable I posessed. Turns out this was a bad move. Swap the cable and voila ... no more noise, silence when editing files, no keyboard crashes, 4.96v / 3.3 v when using my "power bank battery", and 5.03v / 3.3v when using my "2A USB Lenovo Tablet Power Supply". I get similar results with every other USB A-B cable I own  I feel a right muppet for overlooking this.  Regards A Happy Womble |
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| HellbentHorse Regular Member  Joined: 08/07/2020 Location: AustraliaPosts: 55 |
Congrats! I'm sure we've all been subject to muppet-esque oversights before, all part of the learning process right! |
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| Womble Senior Member Joined: 09/07/2020 Location: United KingdomPosts: 267 |
Oh yeah, my feet are full of bullet holes  Wombles have kapok for brains |
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| Atomizer_Zero Senior Member Joined: 04/07/2020 Location: United KingdomPosts: 134 |
I'm glad you've finally worked it out. Now you can code in peace lol |
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bigmik Guru  Joined: 20/06/2011 Location: AustraliaPosts: 2870 |
Hi Womble, Glad you found the cause... Really I am stunned that the cable caused those issues.. I can understand the low voltage, there must be something funny with it for sure.. I have only found that they either work or they dont.. long ones and skinny ones are not generally the best to use.. (albeit the one I use is probably 1.5m (5ft) long and it is running from a USB3 hub that is fed by another 1m feed cable. Kind Regards Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| Womble Senior Member Joined: 09/07/2020 Location: United KingdomPosts: 267 |
You and me both  I had carefully selected the "Newest" and "Fattest" cable I had. It was a known good printer cable approx 1M long. I had considered the cable "girth" and reasoned that a "fat one" would have nice heavy duty conductors. It never crossed my mind that it might be the USB A-B cable. Until Rob stepped in heroically I had assumed it was "assembler" error on my part, or perhaps a duff Waveshare or other component. The number of times I went over my soldering, and checked voltages and went looking for short circuits with a multimeter. I can certainly see why manawyrm specified USB-C for the power cable on his "Clone CMM2 PCB". That connector is designed for charging, and to supply power to devices. Regards A (now) Happy Womble |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2288 |
it was just a process of elimination - i do hope no one was offended as we worked through the list starting at the most probable, working down to the most unlikely. unfortunately, when searching for the root-cause of an issue it is often necessary to ask 'hard' questions, and repeatedly asking them until there is a definitive response. as an aside, try taking a magnet and see if the 'defective' USB cable is attracted to it; i have come across cable from china that is made using steel wires that are copper plated. geoff, peter: might i suggest that checking the 5v rail, between the shell of the keyboard USB socket and the contacts of the power switch, be placed at the top of the list of troubleshooting tips? there may be quite a few USB A-B cables out there waiting to cause CMM2 problems. cheers, rob :-) |
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| Womble Senior Member Joined: 09/07/2020 Location: United KingdomPosts: 267 |
Not me, I'm just A Happy Womble now that I have a fully functional CMM2  |
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| Womble Senior Member Joined: 09/07/2020 Location: United KingdomPosts: 267 |
I agree, also checking the voltage between the USB-B shell and the 5VIN, 5VOUT, and 3.3V pins on the Waveshare was particularly useful to confirm that things are good once you have the CMM2 running initially. |
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64kram Newbie  Joined: 02/08/2020 Location: United KingdomPosts: 2 |
Hi All, just wanted to say a quick thank you for the information in this thread, it's likely saved me a fair few hours! My CMM2 kit arrived this morning and coincidentally I have the same v3.0 PCB model and Waveshare board (from the same Ebay source) as Womble. For my first attempt at soldering I'm overjoyed that everything appears to be working, thanks largely to the details provided here. However I do have the dreaded screen tearing issue, so looks like there's still some work to do! Fantastic product and project. Looking forward to contributing in the near future! |
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| Womble Senior Member Joined: 09/07/2020 Location: United KingdomPosts: 267 |
Well done with the soldering, and welcome to the community. If you have screen tearing, the fix is the Oscillator Mod. I posted the parts I used earlier in this thread. The official RS part numbers are also in the "Construction Guide". There are also posts on this thread about how to approach fitting the mod. Regards Womble |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2288 |
BEFORE doing the oscillator mod, please (a) check the 5v rail (between USB keyboard socket metalwork and back of power switch) and (b) try a different USB A-B cable for the power. i have a sneaking suspicion that bad power may also have something to do with the crystal oscillator on the waveshare module nor running reliably. cheers, rob :-) |
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| pitrz Newbie Joined: 29/09/2020 Location: Czech RepublicPosts: 2 |
Hi guys, have to chime in. Got a waveshare 480MHz and also had to do the oscillator fix to have it working in all modes. With it picture is great! Thanks for all the info here, p. |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9063 |
Just been catching up with this thread, and USB cables have been the cause of lots of trouble for me before the CMM2 even came on the scene. Historically, this tended to be with spinning type external hard-drive units, which would flatly refuse to connect to the PC if you used a sub-standard cable - and I could understand that, but many people just grab the closest cable. This is not so much of an issue now, as more and more external drives move to SSD rather then spinning HDD's that can suck quite a bit of current. One cable I had, was nice and think, but still had the same problem where Windows would refuse to see it when you plugged it in. I swapped it for a brand-new good quality short cable, and the problem went away, so out of interest, I chopped the old thick cable in half, and there were four tiny little enameled copper wires inside a really thick sheath. They were probably about 0.1mm or so thick each - tiny. So, even the thick cables can be misleading, UNLESS you know for a fact that cable X you got from a reliable source. The cheap cables can have a nice thick sheath giving the impression they must use thicker wires, but that is NOT necessarily the case. Voltage-drop is a real PITA, and can cause some really weird results such as have been documented in this thread. After what happened to me as stated above, a few years ago, I went through ALL my USB cables, and binned any that I was suspicious of even slightly. I purchased any new replacements I need from Jaycar, who have their own brand of USB cables. Yes, I even cut one of their ones open to check it, but they used nice thick wires - especially for the power ones, which is where it is most important. Smoke makes things work. When the smoke gets out, it stops! |
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