borfo

PCB - Combined DIN/DOUT x4 modules on one PCB - comments?

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I designed a PCB that combines a DIN x4 and a DOUT x4 on one small PCB.  The modules are connected by traces, so they'll work together in series using the PCB connection, or the board can be split in half so the modules can be used separately.  The board is less than 10x10cm, so it can be printed extremely cheaply at places like DirtyPCBs (~$16 for 10 boards) (I think SEED is offering even cheaper 10 packs of 10x10 boards as well now, but I haven't tried them yet.)  Resistors are mounted on the back of the board.  Ground planes on the front and back of the board, back of the board has a VCC plane zone as well.  Mounting holes match, so modules can be mounted on top of each other if desired.

Anyway, I haven't done much PCB designing, so if anyone happens to notice any errors in this thing before I get them printed, your comments or suggestions would be appreciated.  Once I've done a print run and have tested them, I'll publish the gerbers/brd files, etc. for anyone to use.

MBHP_DIN-DOUTx4-brd.svg

MBHP_DIN-DOUTx4-schematic.pdf

MBHP_DIN-DOUTx4-front.pngMBHP_DIN-DOUTx4-back.pngMBHP_DINDOUT_PCB.png

Edited by borfo

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Hello

 

few things...

-try to avoid 90° angled traces

-try to place capacitor as close as possible to VCC pin of each chips

-why don't you use resistor network to gain space an make routing easier ?

-a common basic practice is to use one side H traces and other V traces, you mix a lot at both side, I'm sure you can optimize a lot of unnecessary via with this simple rule

-dual sided TH component will be a pain to assemble when component hide other side hole, you can place resistor vertically at same side with a 2.54 pitch...

 

Best

Zam

Edited by Zam

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Hrm...  I think I may have spotted an issue actually.  I worked from the smashtv R5 MBHP_DOUT and MBHP_DIN module schematics.  Those schematics show the S0 pin on the DIN module's J1 and J2 to be unconnected, and the S1 pin on the DOUT module's J1 and J2 to be unconnected...  This must be wrong, otherwise the DIN/DOUT chain wouldn't work...  I connected those pins on my board and schematic, but haven't bothered to re-upload the images, etc. in the post above.

 

Are there any other errors in the SmashTV R5 schematics?

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Just now, borfo said:

Are there any other errors in the SmashTV R5 schematics?

Not really an error, mostly to "force" DI and DO Y chaining like.

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Just now, Zam said:

Not really an error, mostly to "force" DI and DO Y chaining like.

Thanks for the reply - could you explain a little more though?  Do the SmashTV boards work in a chain with both DIN and DOUT modules connected in series?  Looks to me as if they must not, since the S0/S1 connections would break (and the RC connections would get mixed up since they seem to be bridged on SmashTV's boards).  By "force Y chaining", do you mean the SmashTV boards force users to split their chain into one physical DOUT chain and one DIN chain?

I'm thinking that for my boards I'll split the RC signals from CORE J8/J9 and connect them through between J1 and J2, and complete the S0/S1 connections so that users could chain their DIN and DOUT boards in series in one single line rather than a Y...  Would there be a problem with that?

Edited by borfo

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It's preferable to not mix Din and Dout in the same chain

So if you want to physically chain two different board you better think like different bus passing through when routing all your digital lines and clocks, so at electric side it's two different (Y) chain

Din and Dout share the same RC1 !

Best

Zam

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24 minutes ago, Zam said:

It's preferable to not mix Din and Dout in the same chain

So if you want to physically chain two different board you better think like different bus passing through when routing all your digital lines and clocks, so at electric side it's two different (Y) chain

Din and Dout share the same RC1 !

...So all I'd have to do to make this board work in one physical chain is connect the S1/S0 connections from J1 to J2 on each module?  I wouldn't have to split the RC connections? (ie: it's ok to leave them bridged?  How about the SC connections?  Are they ok bridged as well? (looks like they're bridged at the CORE, so I imagine they're ok bridged in the chain as well...))  I'd like to be able to have the option of using the boards in one single chain (also would like to make it possible for the two modules on the PCB work in series) - the user could also choose to connect them in a Y if they wanted to.

 

Thanks for the help.

_________________________________

Just noticed your first comment - thanks, those points are totally useful, particularly the H traces on one side and V traces on the other thing...

I guess 90 degree traces are bad because they're more likely to be screwed up in the board manufacturing process?

I didn't use R networks because regular resistors are cheap and I always have lots around, whereas I generally wind up having to order R networks.   I figure all of the parts on these boards are common enough that people often would have them at home already rather than always having to make a special order to make these boards.

Edited by borfo

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OK - I rerouted the board, it's laid out better now.  All components are on top, traces are a bit less of a mess, I added a few 5v/ground headers on each board, and I connected S1/S0 properly so the boards will (or should at least) work in a single chain.

Can someone please confirm it is ok for me to bridge (1) pin 7 to pin 8; and (2) pin 9 to pin 10 (the serial and latch clocks)  on the J1/J2 headers?  Looking at the MBHP_DIO_Matrix schematic, it looks like this should be ok.

 

 

MBHP_DINDOUT-3d.png

MBHP_DINDOUT-front.png

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I've printed a first batch of these boards, and have assembled a couple.  Haven't had time to test them thoroughly, but I figure I may as well post the Gerbers anyway in case anyone wants to print some.  Let me know if they work for you, or if you find any issues.

 

 

mbhp_DINDOUT.zip

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