|
They are OR gates.
AND gates would be idle low so they wont work.
NAND gates would be idle high, but the 1s and 0s of the serial transmission would be inverted, so that wont help.
That is why I went with OR gates - idle high, non-inverted signal, logic 0 to enable, logic 1 to disable.
It seemed like a perfect plan, so i don't know whats going wrong.
Last edited by Kamikaze47; - 6th April 2008 at 14:31.
"I think fish is nice, but then I think that rain is wet, so who am I to judge?" - Douglas Adams
|
Kiss ...
The obvious number is ...
4081 AND Gates ...
or
4052 Triple 2 Input multiplexer
or two series resistors, one to each addressed device ... and grounding ( or VCCing ) the signal ( past the resistor ! ) with another PIC pin , if NO transmission, and use the PIC pin as an input for transmission.
may be too simple ?
Alain
Last edited by Acetronics2; - 6th April 2008 at 14:50.
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
|
I just did a few tests. This idea seems to be working. The signal would not get through the series resistor until i reduced the value to about 200 ohms. That means a 25mA draw whenever the signal is low. I guess that's not too bad.Originally Posted by Acetronics
"I think fish is nice, but then I think that rain is wet, so who am I to judge?" - Douglas Adams
|
The only thing that worries me is the possibility of reduced reliability due to the series resistors.
"I think fish is nice, but then I think that rain is wet, so who am I to judge?" - Douglas Adams
|
74ls 425/426 ???
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
|
Cant seem to find any info on the 74LS425/426 chips.
But I think i'll pick up a 74LS139. The data sheet says its designed for high speed data, so it should be perfect.
I still have no idea why my circuit in my OP does not work tho. As far as I can tell, it should.
"I think fish is nice, but then I think that rain is wet, so who am I to judge?" - Douglas Adams
|
How outlandish is this idea?
I notice you only want to transmit, not receive.
So, how about sending the same data to *both* your recipients, with an extra starting character that acts as a qualifier that decides which of the recipients would accept the data as valid? Assuming, of course, that you are in a position to modify the code at the target units as well.
Regards,
Anand
Members who have read this thread : 0You do not have permission to view the list of names.
Posting Permissions
Bookmarks