Board Revision 1.1.0

[epsilon-0311]

In this issue planned improvements for the board revision 1.0.x are stored:

Schematic topics:

• [x] Add a on/off switch
• [x] remove USB Plug cut out and use a receptacle that is mounted on top Not required due to change to 1.6 mm PCB
• [x] replace 0402 SMD components with 0603 or 0805 ones to ease hand solderability Skipped for now
• [ ] add a protective fuse
• [x] try to find a pin for a dedicated display reset signal - the boot pin is not used after reset
• [x] add a second power LED for the 3.3V output
• [x] remove transistors from resistive touch pad circuit
• [x] try to free pins to get a debug UART interface, probably requires something like a PCA9535PW GPIO Expander
• [x] I rechecked the design guidelines for the ZD1117ILTRAD, the current design works but the resistors should be adapted to meet the guidelines
• [x] improve power supply circuit by replacing the LDO with a buck converter Not required, efficiency is okay, buck converter requires more space and components
• [ ] prepare for SMT assembly
  • • [ ] try to optimise count of different components to reduce component loader fees
  • [x] add an IO expander to free pins of the chip
  • [x] add a buzzer

Layout topics

• [ ] trim size to have dimensions not exceeding credit card size
• [ ] prepare for SMT assembly
• • [ ] add edge rails and fiducials, see here
• [x] replace ground wires with ground pours where possible
• [ ] switch to a 4-layer design with 1.6mm

[epsilon-0311]

the voltage divider should work without the transistor switching the MCU, check if this is possible as it would significantly reduce the component count

[epsilon-0311]

Tested using the voltage divider without the transistor, still works. This should be implemented to reduce component count.