RE: Third Year Systems Project - 3: Begining to look like Something

michaelkellett — Wed, 18 Oct 2017 08:41:35 GMT

Re the serial port.

Normally you would only allow access to a hardware resource to just one module or object of your code.

Any other forms or modules would only get access by calling that.

The way I would design it is for the communications from PC to Mbed to use a strict "command/response" protocol. The PC will send commands and the Mbed will respond. The Mbed will never send a message except in response to a command and it will always respond within a defined (short) time. This allows you to use blocking calls to a "sendcommand" method in your serial comms object (or module or task or whatever).

If you are using threads in c# you can do better and allow many objects to access the "sendcommand" method simultaneously but it gets much more complicated because the serial comms object has to be able to queue the requests and send the responses to the right places.

If more than one object has access to the hardware then there is no reasonable way of sharing the hardware (because you cant tell if some other object just sent a command and is waiting for a reply.)

C# is very big and complicated and offers many ways of dealing with asynchronous communications (that's where you send a command and don't wait for the answer) but you should be able to accomplish all you need with a much simpler (blocking) model.

RE: Third Year Systems Project - 3: Begining to look like Something

DAB — Tue, 17 Oct 2017 17:47:45 GMT

Nice update.

When getting into projects with new tools and software, you always need to allocate some learning time.

Often you discover that what the product promises is different from what the product can deliver.

DAB