SERIN/OUT, SERRXD/TXD Circuits

[Tasp]

When using the above commands ie. connecting 2 x 08m's together for data transfer and send a "GO" command across to start the 2nd chip going, what is the recommended circuit? The manuals seem full of info for connecting everything else except 2 x PicAXE's or am I missing it?

So if I use Pin 2 (Serial In) do I still need the 22k/10k resistor network or should a 10k to 0v then on to the 2nd 08m which also should have a 10k resistor to 0v?

If I don't use the Serial In can I save space on the board and just use a 33k resistor, as I would not be programming the chip once on the board.

Can I use the same pin for IN/OUTPUT, so chip 1 TX's "GO" then issue a SERRXD, 2nd 08m listening on pin 5, RX's the "GO" command, does some code and then TX's back out pin 5. 1 wire data, but will need a 2nd wire for 0v to common supply. Code should be straight forward but resistors required to stop floating one side or both sides?

Sorry if these questions seem daft.

TIA

 

[lbenson]

If not programming, 22K not needed, and 10K to ground will suffice--but for ease of making changes, the extra resistor takes little space when used with a 3-pin programming connection.

Two connections--0V and data--will work if you get the programming right. To protect against the case of having the data pin high on one picaxe and low on the other (which could burn out one or both pins), put a 10K resistor in series between the pins.

 

[jtcurneal]

Serrxd and sertxd only use the serin pin ( leg 2 ) and the serout pin ( leg 7 )

If you want to use serial communication between 2 Picaxe chips, you must cross connect
the serial pins, use a wire from the serin pin ( leg 2 ) on one 08M to the serial out pin ( leg 7 )
on the other 08M and connect the serout pin on the first 08M to the serin pin on the second 08M.
In effect a null modem connection.

Joel

 

[Tasp]

Yes thanks to both, I was aware of the serin/out limitations and the use of null modem type connection, my main concern was the resistor network and ok to ground both pins via 10k.

As for space you'll see what I mean when I post my PCB diagram later!