littleECU and littlePDU

We decided that the most effective way to move forward is to use the e7 prototype boards to try to power the e7 body for this year’s competition alongside most of the e6.5 boards.

littleECU is a mostly universal ECU board, with the following features:

• 2x 12V HSDs (2A each) - for spark and injector
• 2x 5V HSDs (2A each)
• 2 power modes: 12V in and 12V/5V in
• USB 2.0 FS for diagnosis
• 2x 12V 2A fullbridge drivers for small motorized systems (throttle, starter)
• CAN FD passthrough
• BME280 for environmental sensing
• manual toggles (DINs) and diagnosis outputs (DOUTs) through LEDs
• STM32H503 microcontroller with FreeRTOS or bare metal operation
• mini OLED diagnosis display - Adafruit 1.50” I2C 128x128 OLED
• full DFT (design for test) - test pads EVERYWHERE

littlePDU was created to power littleECU using our existing setup - literally just a 4S LiPo. It’s a really crowded board for that reason.

• XT60/XT90 power input
• isolated DCDC conversion to clean 12V and 5V rails
• auxiliary 12V/3V resistor divider outputs
• power monitoring IC & current sensing for all rails

The first iteration of these boards have a few issues though:

• littleECU: 12V HSDs nearly max out capacitive load with onboard 220uF capacitors
• littleECU: tps563200 is very layout sensitive and delivers quite large transient spikes
  • the spikes are big enough to trigger logic on weakly pulled down inputs
• littleECU: zener diodes should be moved before jumpers for enable to protect arbitrary inputs
• littlePDU: PMIC probe traces should be a little more balanced if possible, have to subtract a large offset