Serial to PICAXE via Download Cable

hippy

hippy

Ex-Staff (retired)
Code: 
                                            .----------.
TX  to  PC  <-------------------------------| SO       |
                             ___            |          |
RX from PC  >----.------.---|___|---------->| Ix       |
                 |      |    ___            |          |
                .|,     `---|___|----.----->| SI       |
            22K | |        2 x 22K   |      `----------'
                |_|                  O         PICAXE
                 |                   O
                _|_ 0V              _|_ 0V
This is a simple trick to allow a PICAXE download cable to both program a PICAXE and for the PICAXE to use SERIN to receive from the PC and communicate back with SERTXD ( or SEROUT on 08/08M/14M ). All without unplugging the cable.

Remove link from SI to 0V to enable download.

Link SI to 0V to allow SERIN to function.
 
hippy said:
Code: 
                                            .----------.
TX  to  PC  <-------------------------------| SO       |
                             ___            |          |
RX from PC  >----.------.---|___|---------->| Ix       |
                 |      |    ___            |          |
                .|,     `---|___|----.----->| SI       |
            22K | |        2 x 22K   |      `----------'
                |_|                  O         PICAXE
                 |                   O
                _|_ 0V              _|_ 0V
This is a simple trick to allow a PICAXE download cable to both program a PICAXE and for the PICAXE to use SERIN to receive from the PC and communicate back with SERTXD ( or SEROUT on 08/08M/14M ). All without unplugging the cable.

Remove link from SI to 0V to enable download.

Link SI to 0V to allow SERIN to function.
Click to expand...

Hi hippy may i know what "Ix" stands for? I'm guessing TX to PC would be pin2 and RX from PC would be pin3 on the DB9 connector?

And would it be possible to use anyother output pin besides pin0 to perform the serout command?
 
Hi hippy may i know what "Ix" stands for?

Any input pin, x being the pin number.

I'm guessing TX to PC would be pin2 and RX from PC would be pin3 on the DB9 connector?

That's right, for a 9-way female socket.

And would it be possible to use anyother output pin besides pin0 to perform the serout command?

Pin 0 ( SO on 08/08M ) is used because the cable is used for downloading and it needs to be Pin 0 for that. It is possible to use Pin 0 and any other Pin (Ox) but SO/Pin0 has to be part of the setup or downloading doesn't work. The other advantage of Pin 0 is that's what SERTXD uses so higher speed ( 4800/9600 baud ) transmissions can be used than with SEROUT.

Code: 
                                                  .----------.
TX  to  PC  <----.--------------------.----|<|----| Ox       |
                 |                    |           |          |
                 |                    `----|<|----| SO       |
                 |                 ___            |          |
RX from PC  >----|-----.------.---|___|---------->| Ix       |
                 |     |      |    ___            |          |
                .|.   .|.     `---|___|----.----->| SI       |
            2 x | |   | |        2 x 22K   |      `----------'
            22K |_|   |_|                  O         PICAXE
                 |     |                   O
                _|_   _|_                 _|_ 0V
 
hippy said:
Code: 
                                            .----------.
TX  to  PC  <-------------------------------| SO       |
                             ___            |          |
RX from PC  >----.------.---|___|---------->| Ix       |
                 |      |    ___            |          |
                .|,     `---|___|----.----->| SI       |
            22K | |        2 x 22K   |      `----------'
                |_|                  O         PICAXE
                 |                   O
                _|_ 0V              _|_ 0V
Click to expand...

Hey Hippy I have 2 qns. Why is there a need for an Ix pin for this connection? If my application is to just display temp readings on the PC can I use the serout 0 command?
 
Why is there a need for an Ix pin for this connection? If my application is to just display temp readings on the PC

None whatsoever. The circuit was for a "Serial to PICAXE via Download Cable", extended to allow both SERTXD and SEROUT back to the PC without having to swap cables after download or adding an additional serial to PC interface.

can I use the serout 0 command?

Yes. Just diode mix Output Pin 0 with Serial Out. If it's an 08/08M they are one and the same; simply connect Output Pin 0 / Serial Out to the PC.
 
does the input pins have clamping diodes as well as the rx pin has. if not, then a zener diode between the in pin and the gnd (anode at gnd) is needed. i have looked at the bat85 schottky diode, but didn't look like the right specs.
 
Or add an external clamping diode between input pin and +V. As far as I'm aware that only applies to Input Pin 3 of the 08/08M.
 
hippy said:
Why is there a need for an Ix pin for this connection? If my application is to just display temp readings on the PC

None whatsoever. The circuit was for a "Serial to PICAXE via Download Cable", extended to allow both SERTXD and SEROUT back to the PC without having to swap cables after download or adding an additional serial to PC interface.

can I use the serout 0 command?

Yes. Just diode mix Output Pin 0 with Serial Out. If it's an 08/08M they are one and the same; simply connect Output Pin 0 / Serial Out to the PC.
Click to expand...

Hi Hippy

I do not need to make use of the serin command therefore I can ommit the Ix pin from the circuit right?
 
That's correct. It then becomes a standard download interface ( for the input part) so use the standard 10K/22K.
 
Hi all

Suppose I have an 08M and and a bluetooth chip and both can be configured via the serial cable (TX & RX). Can anyone suggest a switching method where the TX and RX signals be toggled to either the 08M or the bluetooth chip?

Thanks in advance
 
Just use a DPDT ( double-pole, double-throw ) switch ...

Code: 
                   O----------------< From XBee interface
                 /
TX to PC   <---O :     .-------.
                 : O---|---.   `----> To XBee interface
                 :     |   |
                 :     |   |
                 : O---'   `--------< From PICAXE Serial Out
                 /
RX from PC >---O             ___
                   O---.----|___|---> To PICAXE Serial In
                      .|.
                      | |
                      |_|
                      _|_
 
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