Propeller PCB Layout Template and First Attempt
David Betz
Posts: 14,516
Does someone have a template Propeller PCB layout that will work with one of the free layout tools? I'd like to try my hand at designing a simple Propeller board and want to start with a working circuit. I'm really just interested in the Propeller, EEPROM, crystal, a PropPlug port, and any required passives.
Comments
Do you want DIP 40, QFP or QFN?
The thread link above contains DipTrace files for a stripped down Quickstart board. I also have the Propeller Platform SD board files. Both use the QFP, not DIP obviously.
I can also give you my M44D40+ DipTrace file. It can use both the DIP and QFN.
https://forums.parallax.com/discussion/131867/m44d40-propeller-basic-circuit-module-in-dip40-form-factor
You might want to look at Diptrace free version:
https://www.parallax.com/downloads/diptrace-pcb-design-software
Parallax has many Open Source files, (Schematic and PCB) available:
https://www.parallax.com/search?search_api_views_fulltext=Diptrace
Diptrace does Autoroute.
Another thing I wasn't sure about is the difference between ExpressPCB's "Classic" and "Plus" programs. I downloaded the Plus version and it seemed to be able to load the Propeller Platform files. Should I be using the classic version instead?
As an FYI regarding ExpressPCB, if you wanted your gerber to go to another fab house, you will have to pay for it. I don't believe there are any options for you to obtain the design data itself in a transferable format.
ExpressPCB does work together with ExpressSCH, but does not provide linking. See the note on the bottom of this page: https://www.expresspcb.com/expresspcbplus/
Personally, I prefer DipTrace as a free design software. It's very easy to use and several of Parallax's open source designs are done with DipTrace, so it is easy to harvest a board you are familiar with to learn. I actually have the Full version, but the Freeware version has lots of ability.
The "Plus" to me.. is harder to navigate, but does the same as the old program. I'll use to old program if I need to knock out a simple prototype. That's what it is good for.
You could also check into KiCAD (open source CAD) ?
That has a very capable shove router, which is what you really need for compact PCB designs. You steer the trace and the router pushes traces & vias to make room.
The V5 release is very close, but the nightly builds are quite stable.
There is a blog here talking about some CAD decisions..
V5 KiCad is supposed to have a quite mature Eagle importer, but I've not tested that.
A review is here
https://hackaday.com/2018/02/10/whats-coming-in-kicad-version-5/
Google also finds this general PCB design doc, but some links back to here seem to no longer work
https://github.com/rosco-pc/propeller-wiki/wiki/pcbdesign
Google also helps find
http://forums.parallax.com/discussion/116297/redirect/p1
and footprint links in kiCad mentioned here
http://forums.parallax.com/discussion/142380/kicad-schematic-symbols-footprints
and also this link
https://hackaday.io/project/27911-daqiri-a-data-acquisition-and-control-platform
Has files for a Prop based design, that looks to import fine into Kicad v5
and this has SCH symbols already in the LIB for P1 as MCU_Parallax.dcm & MCU_Parallax.lib - looks to include kiCad footprint names (even as far as QFN*44*1EP*9x9mm*Pitch0.65mm* )
https://github.com/KiCad/kicad-library/tree/master/library
oops, and I forgot one of the more important links - Digikey now has a KiCad library activity...
https://github.com/digikey/digikey-kicad-library
Diptrace is only free below some limit, and that seems a quite (deliberately) low limit. 300 pins is not very many.
Parallax uses Altium internally, and that can export via PCAD into kiCAD (which is free, open-source, with no limits)
See the thread
https://forums.parallax.com/discussion/168606/p2-hardware-reference-design-and-choices#latest
for an example simple P2 breakout board - screen shots of it in both Protel99 and KiCad
My report on this gives
#Comment KiCad NET export using PcbNew_Export_PcbNew_NET.py v1.01, from Kicad design: C:/../Parallax/PJ/P2D2-PCAD_M12.kicad_pcb
#Comment: Parts:54, Nets:82, PinsConected:390, TotalPads:399, Ref Skipped:0
So we can see already that breakout board, is above the Diptrace free threshold.
FYI, KiCad loads this file fine too..
Also, when I place the TO-220 version of the LD1085 (actually, LT1085) on my PCB it seems to indicate that the part will be mounted vertically. How do I get a footprint that lies flat so that the heat sink is against the PCB?
And, what header part should I used for the PropPlug. I'm not sure how to decipher part numbers like 644456-4. The -4 part I get but how do I intensify a mail header with the right spacing for the PropPlug?
JMG, yeah, I knew it was 300, but I haven't had to count pins in a while, so I wasn't relating the 300 to any designs. I am very aware of the design you mentioned, and it has a high number of pins for what it is, so yes, it wouldn't work for DipTrace Free. I know that Parallax is using Altium now, but they still have a lot of DipTrace files available on their site. Since I have DipTrace full and know it well enough for designs, I haven't bothered checking out KiCad further. Plus, I have full access to Altium through work (and a friend that knows it very well) if I did want to learn another EDA software.
KiCad is becoming a reputable piece of software though. When I lst checked on their forums (about 6 months ago) the negative thing were similar to the 2.x versions of DipTrace (which is now at 3.2), so I could see DipTrace losing ground if KiCad keeps its current pace of improvement.
I seem to recall there used to be a whole panel of prop boards that you could use either directly or as a model for your project, actually many models. There should be quite a few examples of how different people have designed their prop boards. Can't recall what that board was called, but someone here may remember or have a link to it.
FF
That would be the Sorgasboard:
https://forums.parallax.com/discussion/135920/2012-propeller-community-oshw-smorgasboard-now-at-obcs-propellerpowered/p1
Not all designs were published, and some without BOM.
BTW: For small boards (<4" to a side), seeed studio fusion was the best deal I could find, if you don't mind waiting a few days...
Those LT1085/LT1085 are not cheap as regulators go - do you need a lot of current / voltage ?
I like the look of the new ST LDL1117 series.
Those are like an improved LM317, with fixed outputs, and much lower Iq and low drop out.
Low cost in a SOT223, and with high PSRR, good to 18V, so not as high V or W as the LT1086, but fine for most 9~12V plug power sources.
The low dropout means you can power this from 5V
Don't get caught trying to drive many 100's of milliamps from a 5V linear regulator just because the regulator specs says it can. The more current it handles times the more voltage it is "dropping" is the power it must dissipate which in such a small package and lack of heatsinking can be a source of smoke and woe. So 12V to 5V at a measly 100ma = 7x0.1 = 700mW which is still very hot for small regulators. Use an external 5V or use a switching regulator. Personally I switch down to 5V and use small SOT89 packs or even SOT23 for my 3.3V. There are plenty of cheap 3-pin "7805" style switcher modules available these days, they run nice and cool and being switchers they will draw less current from say 12V then they supply at 5V etc. Rough rule is say 85% efficiency so 5V @ 500ma = 2.5W divided by 12V and by 0.85 is approx 245ma @12V.