With email and Internet news announcements seemingly every day about new MCUs and how they will make your life easier, there has been a subtle change in the background research designers perform when starting a new project. Designers used to ask, “How do I find out about what solutions are available?” Now they tend to ask, “How do I find out how usable these products are?”
Evaluation (eval) kits are one answer. But those, too, have changed. In the "old days", when there were not so many new product offerings, vendors were willing to give you small eval kits without expecting you to immediately place a purchase order for 10,000 pieces. Nowadays, you have to qualify as being ready to buy to get a small eval kit on loan for a month or two. I was lucky that I had the chance to learn about embedded control from the freebies I got 20 years ago. Otherwise I may never have gotten into the business at all.
Even though the freebies are now hard to come by, in their place most vendors offer a plethora of inexpensive eval kits. Many of these kits come with more or less limited development tools (more on that in a later blog) and are so low-priced that I have purchased some myself with my own money, when I really wanted to evaluate a part but did not have an immediate business need. I used my own money because it was just simpler than filling out a lot of company paperwork. My threshold is somewhere between $10 and $50, more likely the former. What you are willing to do with your own money for work may be different.
But there are so many eval kits now available you have another choice to make. Once you have selected a product or a product family to evaluate because it appears to be able to meet your needs, you need to select the eval kit you will purchase. What are the features that will drive your selection?
Some kits are specialized, and intended to let you evaluate specific advanced device features. If your need is to evaluate specific features, and there is an eval kit targeting those features, you are in luck.
Other kits are quite general. These typically are pretty much bare-bones designs with most of the chip’s pins available on connectors or solder pads. Such generalized boards are usually my favorites and have met my needs nicely. Good examples can be found in the Silabs ToolStick family, although many vendors offer similar kits. Let me explain why I like them.
Most Toolsticks are about $10. To program them, you need a USB adapter (Toolstick Base Adapter) that is under $20. The base adapter plugs into the USB connector on your PC and has a socket that mates with a card edge connector found on all Toolsticks. Once you have programmed the Toolstick it can operate without using the base adapter, so you can keep the adapter for use in the next project.
Many Toolsticks contain just the core MCU and simply bring the key I/O pins to connection points on the PCB. Some Toolsticks also have a few additional parts, like a couple of LEDs, a potentiometer, or pads for capacitive touch sensing, to make the sample software examples more interesting. Some have interface chips to implement simple networking features.
Simple software examples available from Silabs demonstrate each peripheral, so it is very easy to understand how each peripheral works and how to configure it. You can combine the examples to build a more complex project, as well. The examples come in individualized versions for each of the chips, and are available both in C and in assembly so that you can be sure that you will always be able to run the examples.
Silabs also has a configuring tool that greatly facilitates the sometimes difficult task of setting up peripherals. Unfortunately, the sample programs do not use the configuring tool, which makes it difficult to go from a sample program to creating an equivalent setup in the configuring tool, but this is a relatively minor gripe.
I find that not only are the Toolsticks neat and inexpensive, they are the best way to evaluate chips that come in leadless packages. Their low price also makes them useful for one-off setups, like creating test jigs or building demos.
Low price, minimal additional hardware, easy I/O access, and plenty of support for learning about MCU peripherals is what makes the Toolstick my favorite evaluation kit. What are your favorite eval kit features and why? Comments invited!