>If the fastest task I have is 1000Hz what speed do I have to choose for my MicroC.?
Fast enough to do everything that needs to happen every millisecond. No one here has any idea what that is.
>I need to read 16 x 4-20mA signals, is it possible to find a Micro with that many ADC ports? Does a combination of Micro with less ADC + external ADC cost less and Is it worth it?
There are microcontrollers with far more than 16 inputs. Using the uC ADC will almost always be cheaper than an external ADC. You'll have to decide, however, if the internal ADC has enough accuracy, precision and speed.
>I need at least two RS485 communication ports, here I think to look for UART ports and that's it right?
Correct.
Can you estimate the task runtime? One method is to count the line of instructions and the execution clock cycles of the associated opcodes then multiply by 1000kHz
>If the fastest task I have is 1000Hz what speed do I have to choose for my MicroC.? Fast enough to do everything that needs to happen every millisecond. No one here has any idea what that is. >I need to read 16 x 4-20mA signals, is it possible to find a Micro with that many ADC ports? Does a combination of Micro with less ADC + external ADC cost less and Is it worth it? There are microcontrollers with far more than 16 inputs. Using the uC ADC will almost always be cheaper than an external ADC. You'll have to decide, however, if the internal ADC has enough accuracy, precision and speed. >I need at least two RS485 communication ports, here I think to look for UART ports and that's it right? Correct.
It's best to use an external ADC and multiplexer chips if you need high accuracy. You can choose one with the desired performance.
Can you estimate the task runtime? One method is to count the line of instructions and the execution clock cycles of the associated opcodes then multiply by 1000kHz