2-XL's new brain will be a stack of the following three boards:

  • Proto Shield (for preamp circuit) w regular male headers
  • Wave Shield with female stacking headers
  • Metro 328 with female headers

For easier wiring, we want the Proto Shield to be on top of the stack, Wave Shield in the middle, and Metro on the bottom. To accommodate this arrangement, we'll need to assemble the boards in a specific way …

Header Swap

projects_male-and-female-headers.jpg
example images of male headers (left) & female stacking headers (right)

The Proto Shield kit includes stacking female headers which we'll solder to the Wave Shield.  We'll then take the male headers from the Wave Shield kit and solder them to the Proto Shield.

So, to assemble these two boards:

  • Follow the Proto Shield's guide - but solder regular male headers pins to the PCB, and omit the 6-pin ICSP male header.

  • Follow the Wave Shield guide - but solder stacking female header pins to the PCB.

Preamp circuit

The Echo's audio out signal is a bit too low for usage on the Metro's analog inputs.  To remedy this, we'll boost the signal using a simple audio amplifier circuit built on the Adafruit Proto Shield.

projects_2xl-preamp.png
preamp schematic

The amplifier uses a classic LM386 audio amplifier IC along with some resistors and capacitors.

While we're at it, we'll also include two additional resistors which will be used for connecting to 2-XL's facial LEDs:

projects_2xl-facialLEDresistors.png
ground connections with resistors for Power LED & Eye LEDs

Layout & Soldering

Using the above layout, mount all the components on the Proto Shield and solder them in place. Solder additional connections (show in green above) on the underside of the board using spare leads or solid core wire.

projects_2xl---proto-solder.jpg
this is me soldering

Next, use solid core jumper wire to make the remaining connections on the top side of the board (seen below in pink).

We'll be soldering more connections to the Proto Shield and Wave Shield later on, but first we'll tend to some software tasks …

This guide was first published on Aug 31, 2017. It was last updated on Aug 31, 2017.

This page (Shield Assembly) was last updated on May 10, 2021.

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