I'd like to know more about how the contact current rating scales with voltage...
The switch I've been using is rated at 0.25 A at 125 VAC... This one is rated at 0.3 A at 6 VDC and 0.1 A at 30 VDC.
Ideally, I'd like a switch that can handle the allowed USB load of 0.5 A at 5 VDC.
Does my 125 VAC switch handle this? Well it does, but maybe it won't last the spec'd number of cycles?
Or, does the 125 VAC rating mean it can handle a lot more at 5 V? I'm not sure...
Anyway, I hope you find a good SMT switch, because I may use it, if it works...
I think I'd leave off the switch entirely, like with the Quickstart... Or else, just leave the pads to mount it, unpopulated...
Took another stroll through Digikey and I think Martin picked out a good switch.
You pay a hefty price to get something rated for more that 300 mA it seems...
Took another stroll through Digikey and I think Martin picked out a good switch.
You pay a hefty price to get something rated for more that 300 mA it seems...
I've used the through-hole version of that switch. It seems pretty solid except that the top plate can pop off.
Jazzed,
Why not add the reset pin between P31 and Vss, as well as/instead of P0 and Vss?
Tubular (not Pedward,)
The idea was to provide a little bit of keying to help prevent boards from being plugged in backwards. Nothing is set in stone at this point.
I got a question, right now I don't bring 28-31 out to the pin header on the PropKey because those are consumed by peripherals. Now that I have a uSD socket, there are 4 pins used by that, with pullups. Do you think I should expose the 4 uSD pins on the socket/header or the 4 other pins?
EDIT: oooh, I got an idea, I'll bring the 4 uSD pins out under where the uSD plugs in and expose the other 4 on the standard header. If you use a uSD, you don't use the pins, but if you use the pins, the uSD isn't plugged in!
I got a question, right now I don't bring 28-31 out to the pin header on the PropKey because those are consumed by peripherals. Now that I have a uSD socket, there are 4 pins used by that, with pullups. Do you think I should expose the 4 uSD pins on the socket/header or the 4 other pins?
EDIT: oooh, I got an idea, I'll bring the 4 uSD pins out under where the uSD plugs in and expose the other 4 on the standard header. If you use a uSD, you don't use the pins, but if you use the pins, the uSD isn't plugged in!
That makes sense. And sometimes you want to mount a SD or uSD socket near the edge of an enclosure. You could see if its possible to take vss/vdd too to make it really easy
Hi guys, I did some layout changes to the PropKey, to include the p28-p31 pins on the layout. I'm really on the fence about this change, since the previous layout is a lot cleaner and less crowded. I was hoping you guys might be able to take a quick comparison look and give me your thoughts in that thread.
With your layout change the pinouts/usage are identical between the PropKey and what you've done. Did you move the uSD to 16-19 so the first 16 port pins are contiguous?
Martin, can I talk you into moving SD back to P0..P3? I think all of my shields use the upper row of pins...
Actually, I bet all existing shields leave P0..P3 alone, expecting SD there...
Also, you'd have software incompatibility with all the existing Prop Platfrom USB code...
It could be routed both ways, with a jumper block to select the pins. I felt there was a real tangible benefit to having p0-p15 available and contiguous, for various interfacing reasons.
1) the inclusion of a protection diode on the power input. A Schottky diode will have a nice low forward volt drop. Reason: I blew a board up due to a faulty walwart that dumped 12V AC into it.
2) moving the crystal further from the regulators. Reason: radio hams are using this board for transmitting and the regulators heat the crystal causing it to drift.
1) the inclusion of a protection diode on the power input. A Schottky diode will have a nice low forward volt drop. Reason: I blew a board up due to a faulty walwart that dumped 12V AC into it.
2) moving the crystal further from the regulators. Reason: radio hams are using this board for transmitting and the regulators heat the crystal causing it to drift.
Cheers
Richard
Who is doing transmitting with the Prop? The crystal drift should only be a problem with direct modulation.
@Pedward. I suspected there would be some controversy over moving the SD card. I was a bit hesitant myself. I had been mulling over using this (or something similar) and a single jumper.
The options I see are
Leave it alone
Switch it permanently to 16-19
Use the 4PDT analog switch
Use a 3x4 block of solder jumpers in a 4PDT arrangement.
(Cheap, but more difficult for the user and requires extra step in mfg to set a default.)
Use a 3x4 male header with 4 movable shunts.
(Huge, may not be room.)
@g3cwi, wouldn't it be a better solution to move the heat away from the crystal instead of the other way around? A simple external power supply fed into the V33 header would accomplish that. The diode is a good idea, I have a stock of those too.
In case you missed it, I vote #1 (leave it on P0..P3).
As an aside, what I would do actually, is leave off the pull-up resistors. That way, it doesn't interfere if somebody want's to use P0..P15 for somethings special.
Or, I see you have the pull-ups as something that could be soldered in after the fact...
@Rayman, I was planning on putting a sip socket at the RP1 location so that the pull-ups can be removed. However maybe just leaving it unpopulated would be better. I've never had any problems without pull-ups.
Somebody said (cluso maybe?) it's actually better without the pullups because there's a way to detect the presense of the card using one of the pins...
Comments
The switch I've been using is rated at 0.25 A at 125 VAC... This one is rated at 0.3 A at 6 VDC and 0.1 A at 30 VDC.
Ideally, I'd like a switch that can handle the allowed USB load of 0.5 A at 5 VDC.
Does my 125 VAC switch handle this? Well it does, but maybe it won't last the spec'd number of cycles?
Or, does the 125 VAC rating mean it can handle a lot more at 5 V? I'm not sure...
Anyway, I hope you find a good SMT switch, because I may use it, if it works...
I think I'd leave off the switch entirely, like with the Quickstart... Or else, just leave the pads to mount it, unpopulated...
You pay a hefty price to get something rated for more that 300 mA it seems...
I've used the through-hole version of that switch. It seems pretty solid except that the top plate can pop off.
Changes made:
- Power switch to SMT
- Reset switch to PTH. (Holes for either straight or right angle.)
- Added 150 ohm resistors to RX/TX between Propeller and FT232.
- Added single 'activity' LED to USB circuit.
- Changed uSD card pull-ups to SIP socket.
- Added reset pins to lower header.
- Adjusted signal traces to 10/10 mil
- Enlarged a few power traces.
- Increased via sizes on power nets.
- Added pads for SMT electrolytic caps while keeping holes for TH caps.
ppusb.zipWhy not add the reset pin between P31 and Vss, as well as/instead of P0 and Vss?
Tubular (not Pedward,)
The idea was to provide a little bit of keying to help prevent boards from being plugged in backwards. Nothing is set in stone at this point.
LOL! The PropKey must've been on your mind!
Ok, so keying is perhaps a good idea. Is there a reason to put the reset pin near P0, rather than P31?
Oh that's right, we talked about that already. Durr
EDIT: oooh, I got an idea, I'll bring the 4 uSD pins out under where the uSD plugs in and expose the other 4 on the standard header. If you use a uSD, you don't use the pins, but if you use the pins, the uSD isn't plugged in!
That makes sense. And sometimes you want to mount a SD or uSD socket near the edge of an enclosure. You could see if its possible to take vss/vdd too to make it really easy
The middle three words seem to be missing. <-- edited.
Jazzed, what do you mean about the middle three words missing?
Thanks Tubular. Seems my brain is on holiday today ....
(This PDF is sans copper pour for clarity.)
ppusb_20120406.pdf
Actually, I bet all existing shields leave P0..P3 alone, expecting SD there...
Also, you'd have software incompatibility with all the existing Prop Platfrom USB code...
1) the inclusion of a protection diode on the power input. A Schottky diode will have a nice low forward volt drop. Reason: I blew a board up due to a faulty walwart that dumped 12V AC into it.
2) moving the crystal further from the regulators. Reason: radio hams are using this board for transmitting and the regulators heat the crystal causing it to drift.
Cheers
Richard
Who is doing transmitting with the Prop? The crystal drift should only be a problem with direct modulation.
e.g. http://blog.g4ilo.com/2012/02/prop-drift-uncovered.html
Cheers
Richard
The options I see are
- Leave it alone
- Switch it permanently to 16-19
- Use the 4PDT analog switch
- Use a 3x4 block of solder jumpers in a 4PDT arrangement.
- Use a 3x4 male header with 4 movable shunts.
@g3cwi, wouldn't it be a better solution to move the heat away from the crystal instead of the other way around? A simple external power supply fed into the V33 header would accomplish that. The diode is a good idea, I have a stock of those too.(Cheap, but more difficult for the user and requires extra step in mfg to set a default.)
(Huge, may not be room.)
As an aside, what I would do actually, is leave off the pull-up resistors. That way, it doesn't interfere if somebody want's to use P0..P15 for somethings special.
Or, I see you have the pull-ups as something that could be soldered in after the fact...
Excellent. Without these changes, may as well not do another board.