It appears on the jpeg that the ground traces on the top outside the Prop narrow down unnecessarily and might trigger a design violation.
Are the vias 0.020? I was thinking that for some development work it would be useful to hack on a reset pushbutton. In that case I'd like one of the vias for reset (either by Q1 or by P6) to be at least 0.028.
Bean, 90 degree corners on high frequency lines are generally avoided in the industry, I think it has something to do with reflections and EMI. Two 45 degree corners are typically used to break it up.
In an impedance controlled trace, having a corner adds some fraction of a picofarad (0.012pF) for an 8 mil trace, and causes a change in the impedance and a reflection (0.3%).· With the trace lengths Terry has on this board, it isn't an issue.·They are short electrically even compared to the fast rise time of the prop outputs.
Thanks Michael, always heard about the subject almost on the level of an urban legend, though it appears where I first heard about it (in a graduate research group creating multi-GHz RF amplifiers) it was a valid concern.
Yes, when things get into the multi GHz, physical layout gets way more critical. Howard makes his living guiding people through that territory.
Thank goodness we have a ways to go before things get too mystical with the Propeller. Although I wonder if we are going to have issues with the next generation. I'm sure bypassing and supply layout is going to be more critical, more stuff switching at a higher speed.
My only suggestion to Terry would be to maybe allow for a bypass cap or two on the back side of the board, right under the Prop, coupled to the VCC lines close to the chip with a via. It wouldn't break up the ground plane much, and would provide a short low inductance bypass path.
But, the proof is in the pudding, and the board is working well with the existing power layout. So maybe my suggestion is overkill.
Hi Terry, great idea for this thing.· Looks to be really handy for travelling, and I really like the possibility to chop off the proto area, solder in a right angle header and plug the whole thing into a breadboard, or a larger piece of perf board for a permanent project.
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MRC
Post Edited (Michael Chadwick) : 6/18/2007 3:03:39 AM GMT
Just ordered my right angle socket. Surprisingly hard to find but pleasantly available in 15way variety, perfect! If you are in the UK you will find them at www.rapidonline.com part: 22-5126
I just realized another great advantage of the dongle concept, I often want to set up an experiment or make a simple but not often used piece of equipment, the demoboard's low price makes this pretty OK but for some smaller projects I can just add a single line of header pins on the vero board or PCB and stick in the dongle when required.
Just looked at your Dongle datasheet. Nicely written.
Notice that it appears resistors on P12..P14 are backwards from 'standard'. I'd always seen/used 1.1K, 560 and 270, whereas your values scale in the opposite direction 220, 470 and 1K. Does that really work well? I didn't think the values were too critical, but a 3x - 4x on the P12 and P14 caught my eye.
Oops, · I have the values backwards. R2 should be the 220 and R4 should be the 1K. · I have fixed and re-posted the datasheet. Thanks for catching that...
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
Here is my Dongle with the side entry sockets and the first "development module", its a TAOS serial 102 pixel linear array that I started to write code for and got sidetracked on. Hopefully I can get some coding time while eating my lunch each day.
I'd run out of the thin layflat heat shrink I had so I've just stuck some sticky back high density neoprene sheet to the bottom of both boards to avoid shorts (bought at local craft store). I've also put a side entry plug on for the video to make it low profile, it does mean I need to use a 90 degree header to make the connection but that's no big deal for me.
Graham,
Nice project.
Be careful because that protoboard doesn't have a PTC fuse that the production units have.
I will send you a production unit as soon as I build a batch up.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
I have a couple of the production unit built. I don't have them on the website yet.
If anyone want to order one (Graham I'll send your tomorrow), just paypal $59.95 to terry@hittconsulting.com. I'll cover the shipping costs for forum members.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
The PropStick USB cannot be used as a stand alone development board. It requires an external power supply and a breadboard to plug it into.
The Prop Dongle IS a stand alone development board, it requires no external power supply and has a (small) prototype area on it.
I'm sure if Parallax had any concerns they would have voiced them by now. (And please do, if you do).
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
I am well aware of the differences!
The idea behind the PropStick is to offer something (nearly) pin compatible to the Propeller with features - as I learnt lately - not easily possbile to integrate within a single chip!
The pricing however ist exorbitant
Your Stick is a trade-off, but not - to my oppinion - a real relief (i.e. a low cost system)
I think both systems - and the Spin Stamp as well - will find their place in a - somewhat limited - market
Just received mine in the mail. Nice job! I plugged it into the Mac running under VirtualPC, ran your blink LED demo program, and--What do you know!--it worked. I'll set it up with a header like Graham's, I think I'll hack in a reset button between the holes next to Q1 and R5. This is going to be a great tool to have on the road.
Graham, That does look cool. Maybe I should think about offering the Prop Dongle in that configuration.
Nice job rounding the corners too.
I'm all out until I get the boards back from Brian (who is doing the populating). So if anyone orders one it will be a week or two before it is shipped.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
Comments
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
It appears on the jpeg that the ground traces on the top outside the Prop narrow down unnecessarily and might trigger a design violation.
Are the vias 0.020? I was thinking that for some development work it would be useful to hack on a reset pushbutton. In that case I'd like one of the vias for reset (either by Q1 or by P6) to be at least 0.028.
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Tracy Allen
www.emesystems.com
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
Post Edited (Paul Baker (Parallax)) : 6/17/2007 6:01:57 PM GMT
http://www.edn.com/article/CA46858.html?q=howard+johnson+right+angle+impedance
http://www.edn.com/contents/images/46858.pdf
In an impedance controlled trace, having a corner adds some fraction of a picofarad (0.012pF) for an 8 mil trace, and causes a change in the impedance and a reflection (0.3%).· With the trace lengths Terry has on this board, it isn't an issue.·They are short electrically even compared to the fast rise time of the prop outputs.
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MRC
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
Yes, when things get into the multi GHz, physical layout gets way more critical. Howard makes his living guiding people through that territory.
Thank goodness we have a ways to go before things get too mystical with the Propeller. Although I wonder if we are going to have issues with the next generation. I'm sure bypassing and supply layout is going to be more critical, more stuff switching at a higher speed.
My only suggestion to Terry would be to maybe allow for a bypass cap or two on the back side of the board, right under the Prop, coupled to the VCC lines close to the chip with a via. It wouldn't break up the ground plane much, and would provide a short low inductance bypass path.
But, the proof is in the pudding, and the board is working well with the existing power layout. So maybe my suggestion is overkill.
Hi Terry, great idea for this thing.· Looks to be really handy for travelling, and I really like the possibility to chop off the proto area, solder in a right angle header and plug the whole thing into a breadboard, or a larger piece of perf board for a permanent project.
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MRC
Post Edited (Michael Chadwick) : 6/18/2007 3:03:39 AM GMT
The boards will be submitted today, and hopefully I'll have some (hand populated) modules ready be friday.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
I just realized another great advantage of the dongle concept, I often want to set up an experiment or make a simple but not often used piece of equipment, the demoboard's low price makes this pretty OK but for some smaller projects I can just add a single line of header pins on the vero board or PCB and stick in the dongle when required.
Graham
I hope to have these for sale very soon.
They will come with an RCA adapter for the TV output, and a 3 foot USB extension cable for $59.95
If you have any questions please ask.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
Post Edited (Bean (Hitt Consulting)) : 6/21/2007 8:37:06 PM GMT
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Problems are the "roads" of life,
solutions are only "onramps" to the next problem
············································· "Brad Smith"
·
I'll let you know when everything is ready.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
·
It was interesting to watch this process.
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Note that I have 1 connection that needs to be cut. If you don't the FTDI chip will overheat if you have a short on the 3.3V power buss.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
Post Edited (Bean (Hitt Consulting)) : 6/22/2007 5:13:53 PM GMT
Notice that it appears resistors on P12..P14 are backwards from 'standard'. I'd always seen/used 1.1K, 560 and 270, whereas your values scale in the opposite direction 220, 470 and 1K. Does that really work well? I didn't think the values were too critical, but a 3x - 4x on the P12 and P14 caught my eye.
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Harley Shanko
h.a.s. designn
· I have the values backwards. R2 should be the 220 and R4 should be the 1K.
· I have fixed and re-posted the datasheet. Thanks for catching that...
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
Post Edited (Bean (Hitt Consulting)) : 6/22/2007 5:14:29 PM GMT
I'd run out of the thin layflat heat shrink I had so I've just stuck some sticky back high density neoprene sheet to the bottom of both boards to avoid shorts (bought at local craft store). I've also put a side entry plug on for the video to make it low profile, it does mean I need to use a 90 degree header to make the connection but that's no big deal for me.
Cheers,
Graham
Nice project.
Be careful because that protoboard doesn't have a PTC fuse that the production units have.
I will send you a production unit as soon as I build a batch up.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
If anyone want to order one (Graham I'll send your tomorrow), just paypal $59.95 to terry@hittconsulting.com. I'll cover the shipping costs for forum members.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
The Prop Dongle IS a stand alone development board, it requires no external power supply and has a (small) prototype area on it.
I'm sure if Parallax had any concerns they would have voiced them by now. (And please do, if you do).
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
The idea behind the PropStick is to offer something (nearly) pin compatible to the Propeller with features - as I learnt lately - not easily possbile to integrate within a single chip!
The pricing however ist exorbitant
Your Stick is a trade-off, but not - to my oppinion - a real relief (i.e. a low cost system)
I think both systems - and the Spin Stamp as well - will find their place in a - somewhat limited - market
Yep, I got it. Thanks for the compliment. I hope you enjoy it.
Now I have to build some more units until Brian can start doing the mass production for me. Yipee... (not).
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
·
Let me know if you do anything spectacular with it.
I updated the datasheet to show a serial LCD example. It works perfectly.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
·
Ordering a dongle today!
Fred2
Again I've modified it for right angled header.
Sweet!
Just received mine in the mail. Nice job! I plugged it into the Mac running under VirtualPC, ran your blink LED demo program, and--What do you know!--it worked. I'll set it up with a header like Graham's, I think I'll hack in a reset button between the holes next to Q1 and R5. This is going to be a great tool to have on the road.
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Tracy Allen
www.emesystems.com
Nice job rounding the corners too.
I'm all out until I get the boards back from Brian (who is doing the populating). So if anyone orders one it will be a week or two before it is shipped.
Bean.
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“The United States is a nation of laws -· poorly written and randomly enforced.” - Frank Zappa
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www.hittconsulting.com
Post Edited (Bean (Hitt Consulting)) : 7/4/2007 12:27:13 AM GMT
Do you have a convenient source for the little 15-pin right-angle header?
Jim C