I will have several devices with atmel microcontrollers which Im going to connect to PC using COM. Is there any way to connect several devices into one COM? (Let's assume COM can handle amounts of data I need to transmit and I can choose the way of sending data using COM)
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Sure, chain the ATmegas together via serial, and use a single USB-serial device. Combine all the data you need to send, and send it out of the single serial port. In each ATmega, you can either relay all the data to the next one, or use a little more intelligent scheme and only forward data meant for other ATmegas.
uint128_t
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Do you suggest to connect microcontrollers in series, so the last one sends data successively through all others microcontrollers and then to PC? (So, each microcontroller should support receiving data and transmitting it to the next chain?) – user3237732 Feb 19 '16 at 11:59
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The standard RS232 COM port does not allow to connect several devices to one port. Because parallel connection of several devices may change electrical signal characteristics such as voltage levels. You may build a chain of ATmegas as uint128_t suggested or change the physical interface type to RS485.
Helen Downs
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I understand that simple 'physical' connection of RS232 cables wont work, I just need a way to solve my problem) Tnx for pointing to RS485, I will check this out – user3237732 Feb 19 '16 at 11:56
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RX pins: you can connect more RX pins together.
TX pins: you can connect more TX pins together if you ensure that only one is active at any time. Others pins must be configured as input or high impedance. This can be done with a suitable protocol.
The parasitic capacitances of pins connected together sum up - this can eventually limit the transfer speed.
Gabriel Cséfalvay
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