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Re^5: Using a controllerless servo on the Raspberry Pi with Perlby afoken (Abbot)
|on Jul 14, 2017 at 15:26 UTC||Need Help??|
I have appended to my post to better explain what I meant.
So, using an AVR or PIC as a "smart" I/O handler (under the control of a Pi or other, similar device) makes a lot of sense.
Yes, that setup can work fine.
But you can also switch the roles of "boss" and "worker". This gives you a microcontroller (like an AVR, PIC, or a "small" ARM) that is nearly instantly up and running as the "boss". It controls the peripherals that connect to the real world (sensors, actuators). It has a small code-base (unlike a full Linux distribution, even an embedded one), so in the worst case, you can and do
Such setups can often be found in medical and laboratory environments, due to standard requirements. Implementing the core functions with hard requirements on a microcontroller is simply much easier than the "messy" environment of conventional operating systems, where processes can be swapped out or blocked by other processes that require memory and / or CPU time. Imagine a life support system that stops working for 10 min to install an OS update package, preventing the control process for the life support hardware from controlling the hardware.
Typical interfaces between microcontroller and computer are RS232 or RS485, because U(S)ARTs are simple and easy devices and require no special hardware on the computer side of the connection. CAN is often used for long connections in noisy environments. And as more and more microcontrollers can behave as USB device and at the same time, RS232 becomes an extinct standard in the PC world, USB is used more and more. Under the hood, USB is often just ending in an FTDI controller that connects to the controller's U(S)ART, so RS232 is not yet dead. IEEE-488 is often found on electrical lab equipment, like power supplies, frequency counters, function generators, multimeters, oscilloscopes, but it is a dying standard that is more and more replaced by USB.
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)