PIC 16F877 with 3 serial ports

[namqn]

If the equipments use RS-232, then the only way to talk to them is via RS-232. That's fine. Your problem can be solved in different ways, depending on the data rate you need.

The baud rate is your communication speed, not the data rate. The data rate is how frequent you want your data. If your data rate is low, like 10 samples/second, then you probably can use some multiplexer to connect the equipments and the host PC to the PIC one-by-one.

If the data rate is high and/or control action is fast, then you probably need a couple of PICs connected together. They can talk to each other via different protocols.

Cheers,

Nguyên văn bởi namqn

If the equipments use RS-232, then the only way to talk to them is via RS-232. That's fine. Your problem can be solved in different ways, depending on the data rate you need.

The baud rate is your communication speed, not the data rate. The data rate is how frequent you want your data. If your data rate is low, like 10 samples/second, then you probably can use some multiplexer to connect the equipments and the host PC one-by-one.

If the data rate is high and/or control action is fast, then you probably need a couple of PICs connected together. They can talk to each other via different protocols.

Cheers,

Thank you very much for your answer, but i want to know how can i do to use the multiplexer to connect the equipments (Multimeter, Barometer) and the card(the card with PIC16F877 to control 2 stepper motors) and the host PC one-by-one.
Do you have a schematic for that? thanks in advance.

Nguyên văn bởi namqn

If the equipments use RS-232, then the only way to talk to them is via RS-232. That's fine. Your problem can be solved in different ways, depending on the data rate you need.

The baud rate is your communication speed, not the data rate. The data rate is how frequent you want your data. If your data rate is low, like 10 samples/second, then you probably can use some multiplexer to connect the equipments and the host PC one-by-one.

If the data rate is high and/or control action is fast, then you probably need a couple of PICs connected together. They can talk to each other via different protocols.

Cheers,

Thank you very much for your reply, but I want to know how to do to use the multiplexer to connect the equipments, the card (the card with pic16f877 to control 2 stepper motors) and the host PC one-by-one, do you have a schematic for that please.
Thanks in advance

[namqn]

For RX signal of PIC, you will need a 3-to-1 multiplexer. For TX signal of PIC, you will need a 1-to-3 demultiplexer.

Have a look at the following links:
http://www.play-hookey.com/digital/m...our_input.html
http://www.play-hookey.com/digital/d...emux_four.html

Remember that you would need 3 separate level shifters (MAX232, for example) in total, when you use commercial multiplexer/demultiplexer chips (because they are logic chips).

Sorry I don't have time to create a schematic for you!

Cheers,