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CB2 micro computer KIT

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granzeier:
One question: with all of the TxD lines tied to only the TxD lines, how does a receiving computer read the data coming from the transmitting computer?
In ULCNet, the Tx and Rx lines are (essentially) tied together so that the data from the transmitting computer will reach all of the other computer's (including its own - so that the sending computer can detect collisions) Rx lines.

granzeier:

--- Quote from: granzeier on November 18, 2019, 01:52:33 am ---One question: with all of the TxD lines tied to only the TxD lines, how does a receiving computer read the data coming from the transmitting computer?
In ULCNet, the Tx and Rx lines are (essentially) tied together so that the data from the transmitting computer will reach all of the other computer's (including its own - so that the sending computer can detect collisions) Rx lines.

--- End quote ---
Never mind; I see that you answered that in reply # 5 - I thought that I had seen that somewhere, but missed it when I looked again.

sv3ora:

--- Quote from: granzeier on November 18, 2019, 01:59:36 am ---
--- Quote from: granzeier on November 18, 2019, 01:52:33 am ---One question: with all of the TxD lines tied to only the TxD lines, how does a receiving computer read the data coming from the transmitting computer?
In ULCNet, the Tx and Rx lines are (essentially) tied together so that the data from the transmitting computer will reach all of the other computer's (including its own - so that the sending computer can detect collisions) Rx lines.

--- End quote ---
Never mind; I see that you answered that in reply # 5 - I thought that I had seen that somewhere, but missed it when I looked again.

--- End quote ---

Not #5 but #7.
The computers where the TX lines are tied toghether, and the RX lines tied together, cannot talk to each other. The ones that have their TX and RX lines tied in a null-modem configuration to the others, can talk to them. If the TX and RX lines are shorted, all the computers can talk to each other, including their own (loopback). By combining these settings (apart from the loopback case) you can do different network configurations.
For example you can have one computer to send to all the others, but to receive from them individually, meaning that the other computers can send to this computer but not send to each other.
And other configurations that I am going to explain in the website.

sv3ora:
Hi,
I have made progress on the LAN networking for the CB2 micros. See here
http://cb2.qrp.gr/extensions/index.html#3_Local_Area_Network
Networking works as designed!

I am going to test the rest of the cases but it's really fun to see all the computers in the LAN to communicate to each other!

Have fun

guenthert:

--- Quote from: sv3ora on November 09, 2019, 03:51:58 pm ---Well, I have just realized this: In the CB2 micro, if you just short the TX and RX lines of the RS232 together, you get the same result as that the article states, without any additional diodes or hardware!

--- End quote ---
Wut?  In RS232 the outbound signals are never tri state.  If you bind them all together there will be trouble.
 You don't want one peer's TX on high connected to another peer's TX on low.

There was a time, when RS422 (one master, multiple slaves) or RS485 (multiple peers) would have been used for such (and might still in industrial settings).

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