Last week, I spent most of my time finalizing the Moo 2.0 schematic design. I have finally made all of the corresponding connections with the rest of the circuit and have a design that I believe is ready to be laid out. Attached is a copy of the current schematic design as of this writing.
I set-up a meeting on Friday to review the design with Ben Ransford, Jeremy Gummeson, and Noah Klugman. They mostly agreed with the methodology and placement of the connections other than a few suggestions regarding the net name nomenclature and placement of the header board signals. I plan on making some slight improvements to the design regarding these suggestions and reviewing the schematic with Noah Klugman one last time. I am hoping to start the layout of the PCB board by Tuesday of this week and have most of it finished by the start of next week.
Notes/Suggestions from the Meeting
- Change board dimensions (make shorter) to account for the reduced pin count of the headers and smaller size of the MCU.
- Maybe move transmit_rfid farther away from the Accelerometer inputs to avoid any noise induced from the higher frequency transmit_rfid signal (640 KHz).
- rearrange external header connections so that it is easier to attach daughter boards for additional sensors (e.g. piezo buzzer, solar panel, etc.)
- consider replacing the analog accelerometer sensor with a more efficient digital sensor from Analog Devices (ADXL362). This accelerometer has a built-in temperature sensor, as well, resulting in a more unified design with less components. It is going to be used on the upcoming Wisp 5.0 design. It will add some additional complexity to get it set-up in software but it may be worth looking into. Since it communicates via SPI, I was think of possibly purchasing breakout board (Sparkfun?) that we can connect to the Moo to test its performance before committing to it. I would like to keep the design changes incremental in case anything may go wrong.
- Talk with Jeremy about the Program Header board. It may have a hardware bug regarding the Vdd connection that will need to be addressed.
- remove the NC (“No Connections”) on the ADXL330. Some are inconsistently connected to ground or Vdd. Verified this with the datasheet and Sparkfun’s breakout board.