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Forum Index : Microcontroller and PC projects : Proto Board for the uMite 28
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Zonker Guru  Joined: 18/08/2012 Location: United StatesPosts: 767 |
Thanks Grogster for the info..!! I will get some ordered today. I hope there isn't any problems or mistakes on the board. I'll stick in an order for 30 of them at Futurlec and see what happens.. I also need to order the FTDI chips and USB connectors... Thanks everyone for all the help with this project..!! 
Now, what kind of format should we use for the 44 pinner..? I think since it is a SMD type part, we should make a board like Geoff's MiniMaximite board. Just plug it into your project and go... Should we include the USB converter on board or not..? Hummm... Maybe some feedback needed... Anyway, it was fun creating the 28 pinner..! I would like to create an TFT MaxiMite board as a main controller with Rs-485 for the uMites also... |
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vegipete Guru Joined: 29/01/2013 Location: CanadaPosts: 1134 |
The trace coming off pin 5 of the FT234 chip looks very close to the pad for pin 6. Maybe push C8 a bit to the right to get a bit more space? Those small ceramic caps are always much smaller than the silkscreen footprint you have drawn. Otherwise looks great! =============== SprintLayout colours are easy to change. Options-General Settings-Colors. Change one of the User colour schemes to whatever you desire. Visit Vegipete's *Mite Library for cool programs. |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Once you get your boards etc, I would be interested in purchasing a kit or fully assembled module, if that is something you may be offering? On the 44, I personally think that the same kind of design as you already have, just with the 44 on-board and the extra IO, would be ideal - you can use the 28 if that is all you need, or you can use the 44 if you need extra IO. All the other connectors and features then remain the same. I like that idea, and I would also keep the 485 and the on-board USB/Serial adaptor too. The only difference being extra header pins for the extra IO, and the 44 on-board as a SMD rather then the skinny DIL. MHO only, others will no doubt chime in with their thoughts. You should be proud of yourself, Zonker - you have designed a lovely little board there.  Smoke makes things work. When the smoke gets out, it stops! |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Well, butter my biscuits Grogs..!! Thanks for the kind words fine Sir. I think your right.. just keep the rest and pop-in the v8 motor... Ok, but should I go total SMD, try to keep the unit as small as possible? Or, keep the through hole parts and keep it easy to build... Humm... Have to think awhile... I will get the 44 pin part created tonight... Also got some board orderin to do... (gitin 30)
EDIT: Thanks Vegipete.. Will take a look at the FTDI chip... On it... |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
On all SMD - MOST people can solder SMD these days. No disrespect to any members who are not happy about using SMD. I was one of them a few years ago, and would not use anything other the through-hole parts, but you just can't beat the price of SMD, and that SMD opens up a whole plethora of new choices of fancy devices you can use. I am happy enough now at 0.8mm(the spacing of the 44), but your FTDI chip at 0.5mm is probably a bit small for my tastes - I guess I just need more practice. 
I have a SMD rework station - perhaps I should use it more. I inherited it with the business when I took over, but have never really needed to use it. I think that the hot-air rework station is ideal when you have those fine-pitch parts such as the 0.5mm, although, EV Blog shows you can solder 0.5mm parts with an iron too, but I have never been quite that adventurous.
Smoke makes things work. When the smoke gets out, it stops! |
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| JohnL Senior Member  Joined: 10/01/2014 Location: SeychellesPosts: 128 |
Zonker you may be interested in this observation that I have posted in another thread. |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Very keen eye vegipete..!!
You are correct Sir, way to close.. got it moved OK.. Thanks John for the info on the transceiver Rx drive..!! I had now idea it would be tri-stated during transmissions... Humm.. does that mean that one could "piggyback" Rx-Tx lines.. Might be useful for all the other things you can use this chip for... Anyway, I stuck in a pull-up on the Rx-IN line... Also made a few more changes during the clean-up pass and have an update to pass out... Keep'em commin Gent's, We will get the roaches out of this thing... NOW..!! Maybe I should hold off the board ordering until everyone takes a final look... Thankyou SHEDsters.. 
2014-02-13_022400_MicroMite_Prototype_Board_update_2.zip |
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| JohnL Senior Member Joined: 10/01/2014 Location: SeychellesPosts: 128 |
Zonker don't forget to add new 4.7K R11 to your schematic. Something else you may want to consider. There is another RS485 tranceiver EXAR - SP3072, this one works from 3.3v supply, has much large fan-out capacity 128 vs 32 for DS3695. Exar also has a lot of protection built in, now I haven't checked DS3695 in detail. One thing I don't like about SP3072 it is only available in SOIC ( no DIP) and is more expensive. Do you have any room on your board to place pads for the soic package as an option. By the way Exar is pin number compatible. I managed to buy decent quantity of SP3072 for about 40% discount recently from Element14/Farnell, they work very well and NO I don't want to sell any. Regards John |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Hey John... The pull-up resistor is in the schematic next to the inverting transistor.. Using Eagle, you have to create the part first, then are allowed to use it in both the schematic and PCB layout. The DS3695 is an old part I had in the library and just used it cause I already had it. You can use any Rs-485 transceiver you want to as they all seem to have the same footprint pin-out. I had a look at adding a SOIC site for the part, but adding the pull-up resistor to the Rx line runs right through the same area... bummer.. I will be using all SMD parts for the 44 pinner design and will fit the SP3072 on that one... Thanks for all your help on this thing John..!! |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Oh my... Here we go again.... I was looking over the PCB the Whitewizard has done and I see that he has pin 4 of the USB connector grounded... Whoops... Mine is not.. I think maybe I need to ground this pin also... I will update the board and post it soon,, Sorry for the mishap... hopefully this should be the last spin... |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
So long as you have not ordered the boards yet! Smoke makes things work. When the smoke gets out, it stops! |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Evening to ya Grogster... Yep, haven't ordered the boars yet.. (thank god).. Not sure what grounding pin 4 does, but mut be something to do with proper USB ID'ing .. Maybe it sets up for v2.0 USB port, not sure.. But if Whitewizzard is doing it... I need to follow along. Anywhy, I got the FTDI chips and USB connectors ordered. I got 30 of each and it set me back $80 sonthin dollars... I got a price of $150 for 30 boards at futurlec, not to bad.. I will get the update out after work on Friday... Startig to look at the 44 pinner... |
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| JTR0701 Regular Member  Joined: 10/07/2013 Location: AustraliaPosts: 71 |
I would be surprised if you were trying to support USB-OTG with this board. It really would complicate things somewhat and is unnecessary as there is no chance that MicroMite Basic is going to support USB-OTG. (BTW. When I say USB-OTG I mean embedded dual HOST/DEVICE mode. ) Therefore... you have it right, don't change it. Pin-4 is the USBID pin for USB-OTG and it is an Input to a USB-OTG capable board. The signaling on this pin is actually done inside the USB cable on the B side. That is that the signal does not appear at the USB-A side connector. If you are not using USB-OTG then it is a NC on the board. If you want the board to be USB-OTG capable then the correct wiring is for USBID to be wired to the pin of the same name on the PIC32MX. (This is pin-14 on a 28-pin dip part from memory...) The USB connector will also need to be a A/B type whereas you are just using a B type. Like I said, this starts to make your simple, easy to use board somewhat complicated. |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Ok.. So leave the pin open, as in don't short it to ground... Humm.. I wonder why the whitewizzard is doing it on his design..? He is using a very similar chip for the USB interface... So... The current "update 2" post of the layout is OK..! (sweet)..! Maybe I can get the 30 boards ordered tomorrow.. Thanks for the info..!
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
I agree, best to leave the USBID floating. Grounding this pin is normally done on one side in the cable to determine the role as there has to be an initial host and device. Here is a good app note from maim: http://www.maximintegrated.com/app-notes/index.mvp/id/1822 Microblocks. Build with logic. |
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| JTR0701 Regular Member Joined: 10/07/2013 Location: AustraliaPosts: 71 |
USB is not the easiest subject and few people really ever delve into it in any great detail therefore it is not uncommon to see minor mistakes like whitewizzard has made, and it is a minor mistake so minor that in the real world it has no effect on anything. The effect we are trying to avoid is you having to respin your board when in fact you have it correct. |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
I would connect pin 1 of the PIC23 to pin 1 of the micromite-interface. External reset possibilities are important. I am still going over the PCB layout at the moment. Microblocks. Build with logic. |
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| Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Yep... Maybe a good idea TZ... That would leave just one ground reference pin to the outside world.. But, if everyone wants the MCLR pin, the change wont be to hard to put in.. I was thinking it wouldn't be needed with the watchdog stuff inside.. OK, deal... I will respin the artwork to include it... Thanks TZ..! 
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
But.... MCLR or RESET or whatever you want to call it, is already there on the board - you can access it easily via the programming header. Afterall, the programming header is only used while programming the firmware, so that done, you remove the programmer, and you can use pins 1 and 3 for MCLR and GND if needed. If it were up to me, I would be inclined to leave it as is - but that is only ME saying that. Smoke makes things work. When the smoke gets out, it stops! |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
I'm glad to see JTR here, helping with USB! John |
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