Re: Parallel Port Propeller?

[Wayne Warthen <wwar...@gmail.com>]

One thing just occurred to me because I have been doing a lot of work with UARTs lately.

Obviously, in the ParPortProp design, there is no way to programatically control DTR or RTS.  The technique I see used frequently in this case is to cross connect DTR with DSR and RTS with CTS.  Essentially, this ensures that the DCE end of the connection will "see" RTS and DSR asserted when it asserts CTS and DTS.  There is no hardware flow control of course, but it could alleviate any issues with the DCE end expecting hardware flow control lines to be asserted.

Looks like there is enough board space to make these cross connects be jumpered which, if done, would be advisable.

Definitely not a big deal, purely an idea to consider.

-Wayne

On Friday, June 15, 2012 9:06:47 AM UTC-7, Wayne Warthen wrote:

Very nice Sergey!

I see that you allowed for the crystal and the 1N3940 to be mounted flat on the board which I very much wanted to keep the board profile low.

One thing which is more of a question than a suggestion.  On the P3/JP2 header, I intend to use a right angle header.  Given the current layout, the pins will extend beyond the board form factor.  Any interest in setting the pins back just far enough that they only extend to the edge of the board form factor when a right angle header is used?

By the way, as far as I can tell, the beta version of RomWBW is working very well with the prototype -- I use it very frequently.

Thanks!

Wayne

On Friday, June 15, 2012 1:28:47 AM UTC-7, Sergey wrote:

Hi,

I uploaded the updated PCB layout and schematics for ParPortProp.

Updates:
- Changed PCB form factor (size, mounting holes, parallel port
connector) to match Zeta SBC.
- Fixed bugs found in the ParPortProp prototype:
    Pin 1 hole of P5 is too small
    Solder mask covers D1 pads on the solder side
    Add pin 1 location marks for P4 and P5
    Connect VGA pin 9 to Vcc
    Check PropPlug pinout (pin 3 & pin 4 reversed?)
    Add a pull up resistor on SD card's CLK signal

Please review.

Thanks,
Sergey

On Jun 5, 12:08 am, Sergey <skis...@gmail.com> wrote:
> Yes, it will be the same size as Zeta. PCB layout is mostly ready. I
> need a few more hours to finalize it.
>
> Thanks,
> Sergey
>
> On Jun 4, 6:08 pm, Doug Wood <whitb...@gmail.com> wrote:
>
>
>
>
>
>
>
> > My vote is for the same size as the Zeta sbc
>
> >                    Thanks
>
> >                           Doug
>
> > On Tuesday, 14 February 2012 14:13:48 UTC-5, Sergey wrote:
>
> > > Here is another idea from "What project Sergey should be doing next"
> > > department: Parallel Port Propeller (PPP, P3?!).
> > > The idea is simple: Connect Propeller chip to N8VEM/Zeta PPI:
> > > - The Propeller will have VGA, PS/2 keyboard, SD card and speaker
> > > interfaces.
> > > - Use PPI mode 2. Mode 2 is bi-directional I/O with handshake. Here is
> > > a more detailed interface description:
> > >  * PPI PA0-PA7 -> Propeller P0-P7 (through current limiting
> > > resistors). Data Input/Output.
> > >  * PPI PC0 -> Propeller P8. Output (input to Propeller) - Command/Data
> > > register select.
> > >  * PPI PC2 -> Propeller RESn. Reset propeller. Might require an
> > > inverter.
> > >  * PPI PC3 -> Header connector (optionally through an open collector
> > > driver). This might be connected to the interrupt line of the CPU or
> > > an interrupt controller, so that interrupt driven I/O can be used. PPI
> > > can be configured to activate this line if there is a byte available
> > > in input buffer or the output buffer is empty.
> > >  * PPI PC4 -> Propeller P9. Input (output from Propeller) - Strobe.
> > > Propeller will pulse this signal when writing to PPI.
> > >  * PPI PC5 -> Propeller P10. Output (input to Propeller) - Input
> > > buffer full. Propeller samples it to determine if PPI’s input buffer
> > > is empty, and it can write another byte to it.
> > >  * PPI PC6 -> Propeller P11. Input (output from Propeller) -
> > > Acknowledge. Propeller will pulse this signal to read data from PPI.
> > >  * PPI PC7 -> Propeller P12. Output (input to Propeller) - Output
> > > buffer full Propeller samples it to determine if there is a command or
> > > data available for it in PPI.
> > >  * PPI PC1, PB0-PB7 - unused. It is possible to provide a header with
> > > these signals, so they can be used for GPIO.
> > >  * Propeller P13 - Speaker control
> > >  * Propeller P14,P15 - Keyboard data and clock.
> > >  * Propeller P16-P23 - VGA signals
> > >  * Propeller P24 - P31 - SD card, PropPlug, serial EEPROM.
> > > - The PCB itself can be pretty small - something like 50 mm x 100 mm
> > > (2” x 4”). I can see it is possible to make mounting holes so that it
> > > can be stacked below a Zeta board or a floppy drive.
>
> > > Advantages:
> > > - Simple interface, PPI handles all the communication, Propeller can
> > > operate completely asynchronously from Z80. Interrupt driven I/O is
> > > possible.
> > > - Compatible with variety of boards (any N8VEM SBC or Zeta board with
> > > PPI). A nice upgrade path for existing Zeta owners.
> > > - Adds video, keyboard, simple sound, and more modern storage options.
>
> > > Disadvantages:
> > > - Uses PPI, so it can’t be used for PPIDE (but hopefully SD card will
> > > replace it).
> > > - A bit more trickier to program than a Propeller directly connected
> > > to the Z80 bus.
>
> > > Thoughts?
>
> > > Best regards,
> > > Sergey