Technical datasheet

2
© 2018 / Bare Conductive Ltd. AW3
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POWER
The Touch Board can be powered via the micro USB connection or from a 3.7V lithium polymer (LiPo) cell
connected to the 2-way JST PH series connector. The power switch will switch the board on or off when
powered by either power source. If power is supplied over USB whilst the LiPo cell is connected, then the
charge LED will illuminate and the LiPo will charge from USB power, regardless of power switch position.
INPUT AND OUTPUT
The Touch Board has the same I/O layout as the Arduino Leonardo, with two important differences.
Firstly, some of the Leonardo pins are used to drive the MPR121, VS1053b and micro SD card. If you want
to use these pins in your project, you can disconnect them from the components they are connected to by
removing the appropriate solder blobs on the board. However, if you do this, you will not be able to use
the functionality provided by the components the pins were connected to, unless you re-make the blobs.
Please reference the Touch Board Pin Map and Touch Board and Shields Guide documents for more
information.
Secondly, there are 12 capacitive touch electrodes, brought out to contacts along the top edge, which
afford connecting through painting, alligator clips or M3 hardware, and a row of 0.1" / 2.54mm pitch pads
on the right side, for you to solder a header to if you wish. 8 of these can be used as digital I/O.
Each special pin function is explained below.
• Touch electrodes These connect to the MPR121 and provide capacitive touch / proximity
E0-E11 sensing. E4-E11 can optionally be used as 3.3V digital inputs or outputs.
• Serial Used to receive (RX) and transmit (TX) TTL serial data using the ATmega32U4
Pins 0 (RX) and 1 (TX) UART. This is separate to the USB serial (CDC) functionality, so the board
effectively has two serial ports — one virtual over USB and one physical.
• TWI (I2C) TWI (I2C) data and clock pins — these are used to communicate
Pins 2 (SDA) and 3 (SCL) with the MPR121.
• IRQ This pin is used to detect interrupt events from the MPR121 —
Pin 4 it should only be congured as an input.
• SD-CS This pin is used to select the micro SD card on the SPI bus. You can disconnect
Pin 5 it from the micro SD card pin for your own use by removing the solder blob
adjacent to the output pad.
• D-CS This pin is used to select the data input on the VS1053b. You can disconnect
Pin 6 it from the VS1053b pin for your own use by removing the solder blob adjacent to
the output pad.
• DREQ This pin is used to detect data request events from the VS1053b.
Pin 7 You can disconnect it from the VS1053b pin for your own use by removing the
solder blob adjacent to the output pad.
• MP3-RST This pin is used to reset the VS1053b. You can disconnect it from the VS1053b
Pin 8 pin for your own use by removing the solder blob adjacent to the output pad.
• MP3-CS This pin is use to select the instruction input on the VS1053b. You can disconnect
Pin 9 it from the VS1053b pin for your own use by removing the solder blob adjacent to
the output pad.
• MIDI IN This pin can be used to pass MIDI data to the VS1053b and have it behave
Pin 10 as a MIDI synthesiser as opposed to an MP3 player. By default, this is not
connected, but you can complete the connection to pin 10 by placing a solder
blob across the pair of rectangular pads provided adjacent to the output pad.
You will also need to place a solder blob on the “MIDI on” pad pair above
the ICSP header.
• HEADPHONE OUTPUT These pins provide the headphone output from the VS1053b on 0.1" / 2.54mm
AGND, R, L pitch pads that you can solder a pin header to if you wish, as an alternative
to the 3.5mm socket.
• EXTERNAL INTERRUPTS These pins can be congured to trigger an interrupt on a low value, a rising
Pins 0, 1, 2, 3, 7 or falling edge, or a change in value.
Continued on next page.