Things to consider for your prototype


One the most exciting, fun and terrifying stages of engineering is when the first prototypes or engineering models arrive in the lab and are ready for testing. You will have been planning for this day for a long time (hopefully) as the cost of identifying and correcting errors later on in the production run only increases.

Planning for this day will have started right back at the concept of the design as you considered how you would test the functionality being designed into the hardware, FPGA and processors etc. Ensuring you have provided sufficient test points and protected them appropriately (you would hate to short out a rail as you tried to measure the voltage). One thing you also need to consider is accessibility of these test points and debug headers to ensure you can actually access them. Another aspect to consider is how you can test the board on its own will you need any special to type test equipment to enable you to test it, when will it be available.

You will also need to compile a test plan to detail everything you intend to test and the expected results otherwise how else can you be expected to know if performs as required or not.

Once you get the hardware in the lab the testing is generally split into two sections the section is checking the hardware integrity i.e. can it be powered on safely and is it suitable for further testing. During this stage you will check the board has been manufactured and populated correctly, that the voltage rails are safe to turn on and then will come the moment of truth when you have to apply power to the board for the first time. This is always a nerve wracking moment…

Once you have applied power you will be looking at the current drawn against your projections, are the clocks at the correct frequency, does the protection circuitry (over voltage / under voltage) resets and sequencing function as desired. This is the basic engineering tests that will be your first priority however; you will soon progress to wanting to test the more complex interfaces and then the performance.

Some of these may be able to be tested via JTAG / Boundary scan however it is only really testing at speed that you can relax a little (you can never truly relax even after all the qualification testing) It is therefore a great idea to have developed some simple test code for your FPGA or microprocessor to prevent you having to debug both the FPGA/Microprocessor design and the board design. I am sure we have all spent many hours looking into is the issue with the board, FPGA, processor or even worse the ASIC.

Once you have completed the integrity checks you can then proceed to testing the functionality and working out what changes you need to make to the next iteration if any.

Of course at some point I am sure you will encounter problems the most important thing to remember at that point is to not panic and attempt to determine the root cause of the issue even if there is nothing you can do about it on the prototype.