PCB layout - JHarvey

[MotoFab]

The 16-bit Pulse Accumulator is just the ticket for an Angle Clock input, for example. If there's any way to use one of the PAs for an Angle Clock input, and still allow an RPM input to the other PA input, it'd be good for future development.

The two 16-bit PA inputs do not have the same hardware. (Fig 7-70, page 356 of the datasheet.)

The Angle Clock prolly would not need the additional features of Port T 7, and can instead use Port T 0. The RPM input could/might make use of the additional hardware features on Port T 7.

I hope I got the pin assignments right this time.

- Jim

[davebmw]

OK Cool thanks guys if there are any other features you want in the CPU area let me know and i'll squeeze them in.

Yeah, put a couple of pins for the bootloader and reset jumpers/switches/headers etc. I like a bootloader switch on the outside of the case and a momentary reset switch is invaluable while testing and messing around. The bootloader needs something but the other one is optional and maybe even a bad idea.

Fred.

No probs, will do

[jharvey]

About the new CPU setup, is that being designed in KICAD? If not can PDF's of the schematic be produced at some point?

Sounds like it's keeping pin for pin compatible with the TA board. If so we could make a board that includes traces for populating the circuit yourself, or purchasing the TA and snapping it in.

Once you have a schematic and things have setteled down, that schematic can replace the current schematic called CPU.sch.

[davebmw]

OK, if i keep the design a drop in alternative for the TA board will there be any copyright issues??

Bear in mind that there will be lots of differences, but it will be pin for pin compatible. i started it on circuit wizard purely because i can use it in my sleep, but then i thought I have to do it in KiCAD as you guys are using it and it would just be easier all round.
If anyone can point me in the right direction as far as designing and linking Schematic and PCB symbols that would be superb!
What i am after are SMT footprints for R/C/L no smaller than 0603, if you have these in a library already linked that would be great.

Anyone that has a TA board, can you provide me with precise dimensions for the positioning of the 2 x 50 way headers?

also the datasheet has specific details on the shape of the ground plane under the MCU, i will try and get the copper fill as spot on as i can, does the TA have this??

are there any more details on the TA board anyone can link to or send by FTP? PM me and i'll provide an FTP account on my server.

cheers!

[Fred]

Guys, I think Dave's TA compatible board should stay Dave's. TA have been good to me with support etc so I definitely don't want to rip them off at all. I can understand why Dave is making one, but I don't think it's right to share them around. Once we have a few designs nailed down, the CPU can go straight onto the board for the keen, and for the non-keen they can buy the TA. I'd rather you were posting rip off schematics of MS boards than TA boards.

However, if you email them and get permission to do it, by all means do.

The TA board does not have the ground plane as you mention etc. It isn't 4 layer as Freescale recommend either, but it does work and it does what we need : be available ready to use.

You should be able to get the dimensions out of KW1252's KiCAD footprint. Otherwise check the downloads section of this site for the schematic, it may give you the dimensions you need too.

Fred.

[davebmw]

After re-reading my thread earlier it sounded a bit misleading, so I'll try to clarify.

I seriously doubt that TA would be at all happy about me copying their design and that is not my intention.

For my own purposes i want to make a separate stand alone CPU card to have a play and learn from the experience much in the way that Fred has with his TA card.

If anyone wants the schematics, PCB layouts BOM or any data from anything I produce, its free for all as in the spirit of this project.

once the schematic is sorted it can be cut and pasted into a main board using the sensor and driver circuits worked on by other members of this forum.

The whole point of this is to have options, to be free to plug a ready made TA module into a high quality PCB containing all the other bits required or have a totally integrated solution with the facility to add extra functionality at a later date, this is what i am after for my own personal project.

My aim is to make this PCB as an alternative with a good choice of options because we should have a choice. the one main thing that pissed me off with MS is the basic generic design that was great if you had a Volvo 240 but really limited for anything designed this side of the sixties.

TA should really be regarded as the holy grail as they brought the XDP512 to us in a manner that is readily available and instantly usable with a few thousand hours of serious coding.

I hope that clears that up, I didn't want you guys thinking I was trying to rip TA off!

[Fred]

I don't and didn't think you were trying to rip anyone off.

I'm happy for you to share xdp512 schematics around and any designs that use it that don't drop in place of the TA can also be shared openly etc. I'd strongly prefer that you didn't publicly share any TA compatible PCB designs though as that is pretty much giving them the single finger salute IMO. Is that fair? Afterall, if you could solder lqfp chips yourself, why would you want to put it on a CPU card?

If we are going to do our own plugin module in the future to keep the cpu separate, we should A design it from scratch, B give it about 200 pins, C use the 144 pin variant or even the XEP and call it FreeEMS2 or something.

Still, you could just call them and ask, it would probably cost similarly and be more of a pain anyway, so they may not mind.

Fred.

[davebmw]

I don't and didn't think you were trying to rip anyone off.

I'm happy for you to share xdp512 schematics around and any designs that use it that don't drop in place of the TA can also be shared openly etc. I'd strongly prefer that you didn't publicly share any TA compatible PCB designs though as that is pretty much giving them the single finger salute IMO. Is that fair?

Absolutely

Afterall, if you could solder lqfp chips yourself, why would you want to put it on a CPU card?

Good point!

If we are going to do our own plugin module in the future to keep the cpu separate, we should A design it from scratch, B give it about 200 pins, C use the 144 pin variant

Strangely enough I have 2 of the 144 pin variety and wanted to do just that, but i want to get the 112 pin (slightly easier to solder by hand) version working first.


or even the XEP and call it FreeEMS2 or something.

Lets plan for the future eh?

Still, you could just call them and ask, it would probably cost similarly and be more of a pain anyway, so they may not mind.

It will certainly cost more as its a one off and will be a pain but its going to be worth it
I will pop them an e-mail just to see what they think.

Fred.

[Fred]

Still, you could just call them and ask, it would probably cost similarly and be more of a pain anyway, so they may not mind.

It will certainly cost more as its a one off and will be a pain but its going to be worth it ;)
I will pop them an e-mail just to see what they think.

I realise why you are doing what you are doing :-) I meant they might not mind you publicising it because no one would bother making it due to the cost and complexity.

Fred.

[jharvey]

What i am after are SMT footprints for R/C/L no smaller than 0603, if you have these in a library already linked that would be great.

KICAD standard library titled libcms includes SM0603, SM0805, and DPAK2 and a bunch of others. Under library discret is R4 which is a fairly normal thru hole resistor.

I'm working on making hybrid versions of the R4 and 0805 package, I'm calling it R4-SM0805 and will be included in A.08 which I should have out shortly.