Bit serial networks.

[hlreed]

If I change my nodes from 8 bit parallel to 8 bit serial I can make them 1/3 cheaper and much smaller, using 4 pin connectors.
With 8 bit parallel, data is always there in the network when you need it.
I don't know if bit serial will even work in a network.
Also I need a two wire protocal. Any ideas on how and whether this would work?
Nodes now, Read data, do function, write data, all in one big loop. Written data stays put until next data arrives.
4 wire is:
1 power
2 control
3 bit data
4 ground
Write now sets control. Read looks at control and reads while on. Don't know if that works.
When I accumulate some money I will try this out, but I am sure someone has perhaps done this already.

[bwts]

Does the power line have 2 B part of the data bus? If not then u could have <p>1 data in
2 data out
3 control
4 signal ground<p>line 2 data out would then link to line 1 data in of the next node and so on.....it may be possible to get rid of the control line by having set length data packages but this would propably limit operation + add uneeded complications 2 the programming.<p>B)

[Colinr]

you have two options either the source node will have to continousally re send the data in a loop untill it changes or the destination node will have to store the last received data. <p>a serial network of nodes was the bases of the now defunct transputer each transputer had 4 bi directional serial interfaces that passed data between each processing block. the interfaces used only three lines GND TX and RX and run at up to 20Mhz.

[hlreed]

Thanks B)
Thanks Colin
I can use 8 pin PICs for this. If they work, my nodes will be smaller than a postage stamp.
To be backwards compatable, The pinouts are:
1 Power
2 ground
3 data
4 control
I will need Parallel to serial and serial to parallel, which is simple.
Nodes are 1 input one output and two input one output. Need pins 1 and 2 for power. Then 4 or 6 pins for data.
Nodes must read, do function then write, so they cannot write continuasly.
I can simulate this with my current nodes. I will let you know what happens.

[hlreed]

I have serial to parallel and parallel to serial working. Number node to PS to SP to display. Only took 5 tries.
I was using 10 pin IDC sockets, ribbon cable and headers on the nodes. Now I need to go to 4 pin and cannot find any.
I can use single inline * * * * or two line
* *
* *
I need pass through, since a cable can be connected to many nodes.
DigiKey has poor pictures and it is hard to see anything that will work.
System is: board to cable to board(s) Boards have headers (easy part), cables need sockets that press on the cables.<p>Any ideas here?

[bwts]

Yep finkin' about it U wouldnt need the control line if U used dedicated TX + RX lines but probably need extra data buffer space for those overload moments.......as for cable what about telephone cable...multicore...plenty of connectors + accesories about......relatively compact....just a thought <p>B)

[hlreed]

Yes, B. Plenty of connectors but not much feed through. I need to be able to send the same data to many readers.
Ribbon cable is light and flexible, expecially with 4 wires.
By the way, I am using 8 pin PICs now. They have enough IO to work. My bit banging system takes 10 clicks (10 microseconds) per 8 bits. Since all nodes work at the same speed, no buffering stuff is needed.
Thanks

[chessman]

Hey Harold, I'll check my JMC catalog when I get home today.<p>I might be able to point you in the right direction, they have enough different types of connectors to fill a warehouse!!!

[hlreed]

I asked AMP if they had any. No they did not. No demand, they said.
What I did was to take a hacksaw to some old 14 pin headers. Two cuts and I have two 4 pin. Same with sockets.
All this has the advantage of having digital and analoq use the same cables and pinouts. I am going ahead with this. It trades time for space.
For example, going from 40 pin PICs to 8 pin PICs.
Price of 12C508A at DigiKey is $.97 each for 25.
Thanks for looking for connectors for me.