MEP EP#338: Feature Complete or Minimal Viable Products

MEP EP#338: Feature Complete or Minimal Viable Products

Project DiffProbe

• Landed on the topology Stephen wants
  
  
  • High voltage dividers
    
    
    • Compensation capacitors
    
    
    • CMRR calibration (120dB rejection)
    
    
    • Offset correction
    
    
    
    
  
  
  • Buffers and Instrumentation Amplifiers
  
  
  • Differential Stage
  
  
  • 10x and 100x attenuation means offsets have to be bang on
  
  
  
  


• Opamps (3 of them)
  
  
  • Buffers
    
    
    • Low input bias current
    
    
    • Low offset
    
    
    • Bandwidth?
    
    
    
    
  
  
  • Differential amp
    
    
    • Low offset. Capable of driving 50 ohm load to the scope
    
    
    
    
  
  
  • Gain setting resistors
    
    
    • Vishay ACAS 0612 - Precision resistor network
    
    
    • 4x0603 resistors to make a diff amplifier with a gain of 2
    
    
    • Relative tolerance of 0.05%
    
    
    • Worst case relative temp-coefficient 15ppm
    
    
    
    
  
  
  
  

Project Snackey

• Firmware is “feature complete”


• Display Commands


• How the vending motors actually work
  
  
  • INA219 Current Sensor
  
  
  • Interrupts
  
  
  • Improved method for next revision?
  
  
  
  


• The one byte Serial Buffer problem
  
  
  • NEOPIXEL (WS2812) vs APA102 (SK9822)
  
  
  • Blocking functions
  
  
  • DMA - Direct memory access
  
  
  • Importance of full system integration testing
  
  
  
  


• Timer Lockouts for motors
  
  
  • Is there a better way?