Simblee Concepts

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Contributors: SFUptownMaker
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General Hardware Information

While the Simblee is, in most respects, very similar to any other Arduino-compatible breakout boards you may have used, there are a few considerations that apply specifically to Simblee-based boards that you should be aware of.

Reduced LED drive strength

This is the big one. A normal Arduino (an Uno R3, say, or a Sparkfun RedBoard) can output up to 20mA into an LED, from more than one pin at a time. Simblee based boards, however, can only drive 15mA total, across all pins. This means you may have to use larger current limiting resistors (something like a 1k-ohm resistor is appropriate) for LEDs with a low forward voltage (like red, yellow, or orange). Attempting to drive too many LEDs at too high a current may damage your Simblee board.

3.3V drive voltage

This has become more common in recent years, but the prevalence of 5V Arduino and Arduino compatible boards still makes it worth mentioning. If you’re not sure of what this means, please refer to our logic level tutorial for more information.

For the LilyPad Simblee and SparkFun Simblee Breakout, we’ve provided some onboard protection circuitry that will allow you to use the 5V FTDI Basic programming adapter (or the LilyPad version) to program them. We recommend against using the 3.3V FTDI Basic (so much that I’m not even going to link to it), as it lacks sufficient supply current to run a Simblee module at programming power levels. Both Simblee boards have onboard power regulation circuitry to convert the 5V power to the 3.3V that the Simblee needs, which brings us to…

Powering your Simblee board

As mentioned above, both Sparkfun Simblee boards have an onboard power regulator to provide the 3.3V regulated power the modules want. A single-cell LiPo battery (such as this one) makes an excellent power supply for Simblee projects; in fact, the LilyPad Simblee not only has a 2mm JST connector specifically to attach to our batteries, it also has an onboard charge circuit!

Of course, as a Bluetooth Low Energy device, we expect the Simblee to have extremely long battery life. This is, however, heavily contingent on the rest of your design. If you are constantly driving LEDs, for instance, or powering an accelerometer or other sensor, you’ll find that the low-power nature of the Simblee module won’t help you much at all. Also, you’ll need to place the Simblee module into a low power mode much of the time to realize the benefits of the BLE power consumption features. More on this later, in the examples section.