Arduino SP0256A-AL2 Shield PCB Build Guide

Here are the build notes for my Arduino SP0256A-AL2 Shield Design.

Warning! I strongly recommend using old or second hand equipment for your experiments.  I am not responsible for any damage to expensive instruments!

If you are new to electronics and microcontrollers, see the Getting Started pages.

Bill of Materials

• Arduino SP0256A-AL2 Shield PCB (GitHub link below)
• 1x SP0256A-AL2 (see notes here on sourcing: SP0256A-AL2 Speech Synthesis)
• Either 1x 3.579545 MHz oscillator (4-pin in 8-pin DIP footprint – see photos)
• Or 1x SI5351 breakout board (see photos)
• 2x 1KΩ resistors
• 3x 100nF ceramic capacitors
• 1x 1uF electrolytic capacitor
• 1x 3.5mm stereo TRS socket (see photos and PCB for footprint)
• 1x set of Arduino headers: 1x 10 pin; 2x 8 pin; 1x 6 pin
• Optional: 1x 28 pin wide DIP socket

Build Steps

Taking a typical “low to high” soldering approach, this is the suggested order of assembly:

• Resistors
• DIP socket (if used) and TRS socket.
• Disc capacitors.
• Electrolytic capacitor.
• 3-way jumper headers.
• Oscillator (if used)
• SI5351 pin headers (if used)
• Arduino headers

It should be decided up front if the board will use a fixed oscillator or a SI5351 programmable clock. Both could be installed, but there is a solder bridge that has to be used to determined which will be used. It isn’t possible to use both at the same time.

This shows the solder bridge configured to use the SI5351. This might be easiest to do prior to soldering other components on the board.

Here are some build photos.

Here is a photo with the oscillator installed, and one with the SI5351 instead.

Note: I didn’t solder the pin headers of the SI5351 to the PCB, but instead used the “fishing line trick” to push the board into the PCB without soldering. This means I have the option of reusing the board again for something else in the future.

By default the SP0256A-AL2 /RESET line is connected to the Arduino RESET pin. It is possible to break this link by cutting the solder bridge shown below and wiring the RESET pad to another Arduino GPIO pin.

Testing

I recommend performing the general tests described here: PCBs.

PCB Errata

There are no known issues with this PCB at this time.

Enhancements:

•  With hindsight it might have been useful to have a jumper option to select the clock mode rather than a solder bridge. But it seemed quite a fundamental choice at the time of designing the PCB that I thought it perhaps shouldn’t be quite so easy to change. Now I’m not so sure!

Find it on GitHub here.

Sample Applications

Here are some applications to get started with:

• Arduino and SP0256A-AL2 (and subsequent parts).

Closing Thoughts

Now it is a bit easier to experiment I can explore a few other musical possibilities.

But this has shown up a slight issue with the chips I have. The highest frequency that the chip can support without locking up seems to be somewhat device dependent.

I’ve seen nothing in the datasheet, application manual, or design guide that suggests it will function at all with anything other than a 3.12MHz oscillator, so I am running it quite a bit out of specification now.

Kevin