Connecting 6 Microcontrollers to a single PC serial port

[kashif_uet]

Dear Friends i am doing my university project the details of which are as follow
i need to develop a system for communication between six clients and one server i.e i have to establish a channel for communication of 6 micro-controllers to a single PC.

And the communication in between must be RS485. I need to develop a working hardware and software. As per hardware portion i have successfully developed RS232 to RS485 converter from a web link (www.circuit-projects.com).

Attached is the image how i have connected my system the problem i am facing is that when i send a data from any of the 6 micro-controllers or from PC it is read by all other connected. i want to establish a system so that if i send a data from PC to say micro-controller # 01 so the data must be read only by micro-controller # 01.

You can say i want to implement some sort of bus topology can anyone guide me in this task.

Thanks in anticipation.

Regards
Kashif
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[wade_hassler]

For messages sent from master(PC) to slaves(uPs) you need to create an addressing protocol in software": ALL slaves read the message, but only ONE responds to it.
Also, any slaves that are not addressed must not occupy your bus: a 'transmit-enable' must be used on each of the six RS232-RS485 converters shown in your diagram

 

[kashif_uet]

Thanks wade_hassler

I have the idea about it but don't know how to do it if you have done any work of this nature do share it with me.

in my case when data is transmitted from PC i can send a byte of address so my micro-controllers will check that if a micro-controller is being addressed that micro-controller will respond but issue is that when two or more micro-controllers want to send data to PC simultaneously what i have to do here to get rid of this issue important is the data lose is not acceptable at any cost.


Thanks in anticipation.

with all kind regards

Kashif

Added after 5 minutes:

Dear wade_hassler


to make thing more clear to you attached is the diagram of my converter here as i see the TX_Enable and RX_Enable pins are short and connected to collector of a transistor that is switch on/off when there is transfer of data.

i will take them out then i am left with 6 extra pins one from each micro-controller then how i will make them working i.e enabling and disabling them using serial port.


Thanks once again.

Regards

Kashif