Nice schematic, I can't wait to see the layout. I know PICAXE chips
(in fact, Microchip microcontrllers) are connected to serial interface
via 3 resistors, no MAX chip between... and everything is just fine. I
used the same thing to transmit data from my chip (12F675) to PC and
also I used a 12F683/PICAXE 08M to upload the program (many times)
into de chip via serial cable with only 3 wires and 3 resistors.:
For receiving pin (no divider):
22K
________
---------------+------|________|----------------> to chip
|
|
_
| |
| | 10K
|_|
|
|
GND
For transmission to PC, a serial resistor of 180R is used. I think
this is a fast and cheap way to receive/send data from/to PC. Is also
secure. And there are many users of PICAXE prepared chips....
Vasi
On Jul 20, 10:42 pm, Sebastien Lelong <[email protected]>
wrote:
> Hi guys,
>
> I tried to draw a schematic for this Jaluino board, 18F4550 based, but
> this is not my "cup of tea"... Attached is a picture + eagle
> schematic, showing the whole:
>
> Few questions/remarks:
> - For now, I put two jumpers for I²C resistors. Joep I understood
> you'd put pad so users can solder it or not, whether they want i2c. I
> would prefer a reversible solution..
> - I took as much as I could from Albert & Richard's 18F14K5°
> schematic about USB, but I'm not sure it's all correct...
> - I still need to put some parts for Tiny bootloader software reset.
> Has anyone already experienced this feature ?
> - about ISCP: connector has a Vcc pin. Is it +5V ? Or the power
> supplied by the programmer (something like 12/13V) ? I've consider Vcc
> as a third power supply, with +9V (from battery of wallmart power
> supply) and +5V, produced from 9V or USB.
> - I still need to put connectors for all pins. My question is: do we
> want to put all pins in connectors, even those already involved in
> something ? Ex: pin TX is involved in serial. Should this pin be
> connected to a connector, thus exported to user, or not ?
>
> Can you guys give a look at it ? Any comments ? Ideas ?
> Maybe Richard Zengerink could help us with that, as he's our
> schematic/PCB guru... Richard ?
>
> Cheers,
> Seb
>
> --
> Sébastien Lelonghttp://www.sirloon.nethttp://sirbot.org
>
> > 2009/7/20 Sebastien Lelong <[email protected]>:
>
> >>> And if we do none of the above, we can have a 4-pin header:
> >>> - ground
> >>> - 5v
> >>> - tx
> >>> - rx
> >>> Cheap, small and still ease to access serial port (with only one
> >>> convertor you like for all your boards).
> > These are the lower 4 pins of the 8-pin connector you see on all my
> > boards. The upper 8 are for ICP.
>
> >>> > - I²C: alsways a must. An "I²C ready" board allows many experiments
> >>> > and is opened to many 3rdparty chips.
> >>> I propose a 5-pin header here with the following layout:
> >>> - ground
> >>> - scl
> >>> - sda
> >>> - 5v (= regulated ps of pic)
> >>> - 9v (= unregulated input ps)
>
> >> Looks ok for me. With such a standardized connector, we'll able to easily
> >> plug multiple jaluino boards together...
> > Again, I have a lot of experience with this kind of layout. Especially
> > the combitation of the two power supplies well surprisingly. It can be
> > used for power distribution at both levels within the same system. And
> > since it are different pins, mistakes result in system parts not
> > having power, not releasing smoke ;)
>
> >>> And optional pull-up resistors.
>
> >> You mean, with a jumper ?
>
> > At least a place to put them. Jumpers (you need 2) may be overkill
> > (you can put a 2-pin header at the resistor's place and put the
> > resistors on there if you to switch often). Two soldering pads could
> > be usefull if the space is there.
>
> > Joep
>
>
>
> jauino_alpha.sch
> 79KViewDownload
>
> jaluino_sch1.png
> 43KViewDownload
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