After creating the initial prototype of the talking ruler and considering some of the early feedback given to me by people who have seen the device work, the new version is now on its way. This is now a self-contained unit that includes speakers, audio player, microcontroller and battery.
The first version of the talking ruler worked quite effectively and produced a good clear sound, but suffered from having external wires, an external microcontroller and audio player:
As the image above shows, the first version of RixTalk used an Arduino Uno R3 together with the brilliant Adafruit MP3 player shield (super audio quality). A standard HB pencil was wired to the Uno via a simple 3D printed cap, and the contact points on the ruler (that are touched by the pencil) are wired to the analog ports. It worked well, but was rather cumbersome with all the external wires and external microcontoller.
The new version of RixTalk (let’s call it RixTalk2) is self-contained, with the speakers integrated into the ruler itself, and all electronics contained within a housing that is screwed to the ruler. The new version uses digital ports on the Pico, as there were not enough analog ports available. All of the components are 3D printed using a Prusa Mk4S.
Note that the first notch on the ruler is a locater for 0 mm. The remaining notches are either large (every 10mm) or small (between each large notch). The large notches represent lengths at 10mm, 20mm, 30mm, etc., and play audio sounds for each one. The small notches are for lengths 5mm, 15mm, 25mm, etc., but do not play sounds.
Internally, the microcontroller is a standard Raspberry Pi Pico Mk2 (i.e. not wireless), the MP3 decoding and playback is taken care of by a Fermion MP3 module, using simple AT (ATtention) commands via one of the UARTs on the Pico:
The Fermion is connected to a pair of 2W speakers that are located at either end of the ruler, and is controlled directly by the Pico. Both Pico and MP3 player are powered using a single 3.7V 150 mAh LIPO battery that is connected to an Adafruit lipo charger module:
The Pico and Fermion site side-by-side on a piece of stripboard (not the nice little Pi Hut board above – that was too small), which is used to connect everything together.
The audio was generated using an AI text to speech engine, with an English sounding female voice. Each number was generated individually and stored as an MP3 file on the Fermion player.
The image below shows the RixTalk talking ruler assembled, together with a 3B pencil. A 3B is being used as it gives better conductivity.
The talking ruler has yet to be tested out with end users, but that should not be too far ahead.