Touch display with RGB silicone buttons for Bus Pirate Ultra

This is the prototype display board for the next, and possibly final, revision of Bus Pirate “Ultra” v1. We went a bit wild, but we’re thrilled at the possibilities:

  • 2.8″ IPS LCD with capacitive touch display. The capacitive touch sensor is I2C based, so we added an I2C bus and interrupt pin to the flex connector
  • 2 silicone buttons with an RGB LED under each. The buttons are read through a TCA9534 I2C IO expander, basically a 5volt tolerant PCF8574 at half the price. The TCA9534 uses the same I2C bus as the capacitive touch sensor, and gets a dedicated interrupt signal on the flex connector
  • SK9822 RGB LEDs share an SPI bus with the LCD. The SK9822 runs at 5volts and uses a two pin protocol that can be driven by an SPI peripheral, but it doesn’t have a chip select pin so it can’t share an SPI bus with other slaves. We use a 74HCT573 as a level converter (3.3->5volts), and the 573’s latch pin as a pseudo chip select
  • The board is now powered from VUSB (5volts) and has a 3.3volt regulator
  • 6 additional IOs (routing in progress) from the unused pins of the TCA9534

A few tweaks to the schematic before we send off the PCBs:
*MISO on SPI should be jumpered. This leaves a disconnected pin between VUSB (5volts) and the 3.3volt logic pins
*Route unused IO pins to a header
*Run LCD backlight from VUSB

v1e is nearly complete and we’ll make a small batch of them soon, but probably immediately after spring festival. Feels free to hit us up on Twitter or check out the latest in the forum.

from Dangerous Prototypes https://ift.tt/2FbhRPn