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With the board described here, we will interface the electrode board for gesture recognition to Arduino.
To take advantage of the potential of the MGC3130 integrated circuit, we thought of developing a new electrode having the possibility to connect (in addition to our demo board, that we saw in the previous episode), even to Arduino Uno Rev3 board (or to Arduino Leonardo Rev3). Moreover, the new electrode has been thought and designed, so to be able to connect even Raspberry Pi boards and in particular Raspberry Pi B+ or Raspberry Pi 2 boards.
Obviously, only one of the abovementioned boards may be connected directly to the electrode board; in other words, if we decide to work with Arduino world we cannot connect Raspberry Pi as well, and vice versa. It is understood that the matter of connection uniqueness is still valid for our board as well.
Let’s start by describing the electrical diagram of our new electrode by starting from the MGC3130 integrated circuit, which is configured to manage five receiving electrodes (RX) and a transmission electrode (TX).
The communication interface used by the MGC3130 integrated circuit is the usual I2C bus, plus there are two communication lines: TS (EIO0) and RESET. It is brought both to the connection interface towards Arduino’s boards (U2) and to Raspberry Pi’s connection interface (U3). Such lines are obviously brought to the CN1 and CN2 connectors as well, for the connection of our demo board. Given that the MGC3130 is powered by +3,3 Vcc, it is needed to adapt the signal towards Arduino electronics, since those are powered by +5 Vcc. The line matching is made by taking advantage of the BSS123 MOSFETs at the channel N (Q1, Q2 e Q3).
There’s no need to adjust the I²C BUS lines that are brought to our demo board and to Raspberry Pi, since the electronic parts operate at +3,3 V and are compatible with the MGC3130 integrated circuit.
Three buttons (P1, P2 e P3) and a jumper are connected both to Arduino’s board and to Raspberry Pi’s one. They are used to reproduce the functions that have been implemented on our demo board.
Pull-up resistors have not been arranged, since they are already integrated in Arduino board as well as in Raspberry Pi. In fact, it is possible to activate them via code when configuring the microcontroller’s pins as inputs.
Both for Arduino and for Raspberry Pi board we prepared a LED signal, respectively LD7 for Arduino and LD8 for Raspberry Pi. It is useful during the gesture recognition, or for the management when pressing the P1, P2 and P3 buttons.
With this new board we also took the opportunity to take advantage of the extended I/Os (EIO2, EIO3, EIO6 and EIO7), to which we connected the LEDs in order to inform about the detected gestures.
During the parameterization, it is also possible to decide which gesture will have to be monitored and returned on one of the possible outputs, or to a combination of them. For our application we chose to return the following gestures to the LEDs:
- Flick West – East;
- Flick East – West;
- Flick North – South;
- Flick South – North;
- Single Tap North;
- Single Tap South;
- Single Tap West;
- Single Tap East;
- Single Tap Centre;
- Clock Wise;
- Counter Clock Wise.
