Hi Albert, And many thanks for this ! For now, I think I'll go with solution B, which is the one I understand the most...
Seb 2009/7/25 a.faber <[email protected]> > Hi Seb, > Attached 4 possible solutions > > Solution A: Almost the current solution, except added a bypass diode across > the 7805, so it won't blow up if there is USB 5V and not external 9v > Solution B: Current solution, except make power selection via a jumper > selection (less user friendly, no voltage drop) > Solution C: Auto power selection via 2 schottky diodes (drawback, voltage > drop of ~0.3v) > Soltionn D: Auto power selection with self power dominance (drawback, > voltage drop of ~0.3v) > > General remarks: > D6, D7, D10, D11 in my schematic does not have to be a schottky type if the > external supply is > ~8V > L1,L2,L3,L4 (ferrite bead, or power choke), not realy required, but > recommended > > > Albert > > ----- Original Message ----- > From: "Sebastien Lelong" <[email protected]> > To: <[email protected]> > Sent: Saturday, July 25, 2009 12:42 PM > Subject: [jallib] Re: jaluino (first schematic... Richard ?) > > > Hi Albert, > > I tried to do some research, but I'm lost, this is far beyond my > understanding and I can't figure out how to deal with self-power USB... I > need your help, would you mind giving me an example of self-powered USB vs. > not self-power USB ? Your 18F14K50 PIC is self-power isn't ? I can't see > the > difference with my schematic... > > Also, I've found something about using a shottky diode to select +5V from > regulator or +5V from USB (see picture, part of schematic from an Arduino > board). Is that what you were talking about ? > > > Cheers, > Seb > > 2009/7/23 [email protected] <[email protected]> > > > > > Hi Seb, > > Some comments on the schematic: > > > > In the current schematic the 5V and USB-5V are connected, this is not > > according to spec, > > see also the datasheet about USB self-powering. Either way, use a > > jumper selection for the > > power supply or use some shottky diodes, in addition it might be wise > > to place a by-pass diode > > across the 7805, since these devices don't like to be reversed > > powered. > > > > Why R1? I think you can remove it, since the reset pin is held high > > via R5/D2 > > > > Be sure to put a 100n bypass close to VSS/VDD pins of the PIC, I don't > > know if C2 is the PIC bypass cap, if so I would > > draw it closely to the PIC VSS/VDD pins > > > > > > BTW, the 18f14k50 board is working fine > > > > Albert > > > > > > On Jul 22, 9:37 pm, Sebastien Lelong <[email protected]> > > wrote: > > > Some more thoughts about Jaluino (next guy who talk about math lib, can > > you > > > modify the subject plz ?)... > > > > > > The connector's layout is very important, as all shields will have to > be > > > compatible, and will reproduce this layout. > > > For instance, Arduino diecimila has 4 connectors: > > > > > > - 2 on on this upper side > > > - 2 on the bottom side, 1 being reserved to power > > > > > > Arduino mega uses a much bigger AVR than Diecimila. They put a double > > > row > > > connector, on the right side. Still, the four previous connectors are > on > > the > > > same place. As a consequence, shield for Diecimila can be used with > > > Mega. > > > > > > I'd like to reproduce the same. If we build first Jaluino board, > > > 18F2550, > > it > > > could have the same connectors as in Arduino (2 on upper side, 2 on > > bottom > > > side). Next step is a 18F4550 based board. We could add a single row > > > connector on the right. In the future, if we decide an even bigger PIC, > > > we'll be able to double this left connector. > > > > > > That said, I still can't produce a PCB, I'm having a lot of trouble > > placing > > > parts to avoid vias... Any PCB guru here ? > > > > > > PS: as a bonus (...) here's my last schematic, with connectors. > > > > > > Cheers, > > > Seb > > > > > > 2009/7/21 Sebastien Lelong <[email protected]> > > > > > > > > > > > > > > > > > > > First try to get a PCB layout gives way too much vias. This is where > I > > > > spend days to get a decent PCB... > > > > > > > Seb > > > > > > > 2009/7/21 funlw65 <[email protected]>: > > > > > > > > On Jul 21, 7:49 pm, Sebastien Lelong <[email protected]> > > > > > wrote: > > > > >> I think this assumes the peripheral on the other side (eg. a PC) > > > > understands > > > > >> RS232 level between 0 and 5V, instead of -12V and +12V. It's > > sometime > > > > the > > > > >> case, and to be sure, using a MAX232 chip is better. That said, > > > > >> with > > the > > > > >> "plug your own serial module" option, you can choose whatever you > > want. > > > > This > > > > >> gives a fourth option, a the cheap side, so we new have: > > > > > > > >> - FTDI chip based USB-to-serial adaptor > > > > >> - 18F14K50 based USB-to-serial adaptor > > > > >> - MAX232 based, with DB9 connector > > > > >> - resistor based, with DB9 connector > > > > >> - (and last option: "my own way to deal with serial") > > > > > > > > Ok, not on board, but I thought they can be disabled by jumpers, > and > > > > > can be a fast solution to test the software but yes, is not a good > > > > > ideea. > > > > > > > >> Some more thoughts about the board. Original Arduino Diecimila > uses > > a > > > > >> Atmega168, a 28-pins chip. > > > > >> See:http://arduino.cc/en/Main/ArduinoBoardDiecimila. From this, > 20 > > pins > > > > >> are "exported" through connectors on sides, where 2 pin are > > dedicated to > > > > >> RX/TX, thus involved in board's functionality (I mean there aren't > > > > >> completely free, as they are involved in serial). > > > > > > > > I don't know, maybe others have more ideas. First, I looked at > > > > > ATmega168 pins, to see some similarities at ports level but I think > > > > > the key is at software level. And is the only level where Pinguino > > > > > offers Arduino compatibility (and maybe the reason why the author > > > > > didn't offered a shielded variant). > > > > > For "reusing" Arduino shields, I think a study must be done. > > > > > Studying > > > > > different shields with their software to see how interact with the > > > > > board. In what manner are used digital pins, etc. ... Because I > > > > > don't > > > > > think they take in account very much the particularities of the > chip > > > > > himself (I think the software is hiding the hardware). > > > > > Maybe is too much work but a shielded board is a must, even if not > > > > > Arduino compatible. This is jallib team decision, and I hope a good > > > > > board will increase the number of programmers using jal language > > > > > (unfortunately, the fact that jal don't have a math library is > > another > > > > > obstacle regarding to "mass" adoption - the new comers remain with > > > > > basic languages and advanced people go to C language). > > > > > > > -- > > > > Sbastien Lelong > > > >http://www.sirloon.net > > > >http://sirbot.org > > > > > > -- > > > Sbastien Lelonghttp://www.sirloon.nethttp://sirbot.org > > > > > > jaluino_sch2.png > > > 56KViewDownload- Hide quoted text - > > > > > > - Show quoted text - > > > > > > > > -- > Sbastien Lelong > http://www.sirloon.net > http://sirbot.org > > > > > > -- Sébastien Lelong http://www.sirloon.net http://sirbot.org --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "jallib" group. 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