Due Dates:

• Schematic - 9/27/25

• Layout - 10/4/25

• Rev. A Ordered - 10/13/25

• Firmware/Testing - 11/1/25

Description/Purpose

• We are using the Elcon HK-MF-108-32 charger to quickly charge the car’s main battery pack during drive/test days. This interface board handles CAN communication between the battery and charger, along with powering the BPS and displaying telemetry data.

Requirements

• Boost converter (12->24v) for low voltage output of the Elcon charger to power the BPS. Should have power protection (reverse polarity, overvoltage, overcurrent, etc.) on both the input and output side of converter. And a fuse cause lakslay :D

• Uses a LeaderSOM for MCU and CAN circuitry

• 2 CAN buses - CarCAN and Elcon, to separate the charger bus from the BPS (LSOM has 2 buses you can use)

• Display to view BPS and charger telemetry (voltage, charge current, SoC)

• Send/receive all charger CAN messages as defined in Elcon protocol

• Display voltage of highest/lowest module, Elcon current reading, BPS current reading, avg pack temp, highest module temp, any faults. Ideally easy to see in sunlight.

• LED indicators for high-voltage active, fault, etc. Buzzer/sound indication for when charging is complete or something is blowing up…

• E-stop button to halt charging and trip BPS when pressed

Application Note

• Elcon datasheet

• CAN message interface

Open

Open

Context

Location of the board:

Connection List

Main

Schematics

Overall Schematic:

12V-24V Boost Converter:

RPP/OV:

SPI Display:

LEDs:

Layout

Github link: Github

Image:

PCB:

3D Model:

Firmware

Drivers

High-Level (Block Diagram)

RevA Testing Process/Reflections:

Overall Design Feedback:

• RPP wont work since the inverse current flowing through the Z1 and Z2 diode, creating another a current path, shorting the circuit

  • Remove Z1 and Z2 diode on v2 of board

• Overvoltage protection will work

  • As long as power <1 Watt

• Diode needs to be WAY above the OV threshold

  • Fuse Voltage threshold for 24V circuit: 31.50V

  • Overvoltage setting on IC: 30.319V

  • Fuse Voltage threshold for 12V circuit: 15.75V

  • Overvoltage setting on IC: 14.91V

• Remove R13 from Vin to VS on the 12V RPP chip or change to 0 ohms jumper because it never turns the IC fully on

• Add test points for every single IC pin, that way I can bridge stuff together and for easier testing

  • Esp the BOOST CONVERTER FAHHHH FUHHH

• VCAP to VS voltage must be greater than the undervoltage lockout voltage (6.5V) for the RPP/OV IC to turn on

• MOSFET never fully powered on in the 12V RPP circuit

• Add throughole test points to solder wires and test at the same time, easier to isolate the circuit

• Add a 12V input test point after the 12V RPP/OV circuit to manually input 12V to test 24V output easier

Design Changes for RevB:

• ADD:

  • Proximity Pilot Pin Control Pilot Pin

  • Status LEDs to mount onto the faceplate

    • Constraints:

    • LED Hole Diameters/Color

    • Operating Voltage (12V-24V)

• REMOVE:

  • TBD

Soldering Issues:

• 4.7uH inductor footprint sizing affects soldering capacitors and other components

  • Add test points for the pads under the inductor

• Choose a bigger boost converter, the current boost converter has the possibility of shorts underneath it, easier solder pins. 

  • Make sure to add testing points for each of the pins

• Hard to debug before the boost converter because of lack of test points

• Hard to debug because the continuity points are hard to remove such as the SMD boost converter

• Add more images to cover up blank space

• NMOS possibile short + trace blown (Validated, trace is NOT blown)

• Check for resistance between components and high points

• Use power calculator based on output voltage to have max current 

  • Power resistors put it on the board 

Testing:

• SPI Display: success ✅

  • 3.3V @ 1mA, drawing 0.180 watts

• Boost converter status:

  • v1 Testing: success ✅

    • Cause of prev failure: unable to read 12V from RPP/OV circuit

  • v2 Testing: failed ❌

    • something is clamping output voltage

• 12V RPP status: failed ❌

  • Cause of failure: Zener diode at the input

• 12V OV status: success ✅

  • OV threshold @ 14.84V

• 24V RPP status: failed ❌

  • Cause of failure: Zener diode at the input

• 24V OV status @ 1mA, OV activated @ 28.4: success ✅

  • 12V: success

  • 16V: success

  • 18V: success

  • 26V: success

  • 28V: success

  • 28.4V: success

  • 28.5V: failed

  • 28.6V: failed

  • 29V: failed

Firmware Plan:
/App

  main.c

  system_clock.c        // SystemClock_Config()

  board_pins.h          // all pin/AF defines for THIS PCB

  common.h/.c           // fault bitmap, shared types, helpers, error_handler()

/Drivers

  display_spi.h/.c      // SPI driver & reset pin for display

  estop.h/.c            // E-STOP input

  leds.h/.c             // 4 Status LEDs (GPIO)

  buzzer.h/.c           // PWM

  can_car.h/.c          // CarCAN specifics

  can_elcon.h/.c        // Elcon protocol

/App

  task_display.h/.c     // render telemetry onto display

  task_led_buzzer.h/.c  // blinks/tones from events and test PWM of buzzer

  task_can_rx.h/.c      // both buses, Rx parse -> queues

  task_can_tx.h/.c      // periodic Tx (requests/heartbeats)

  task_ESTOP.h/.c      // E-STOP handling

  task_telemetry.h/.c   // aggregates latest values for display/LEDs

Circuit Components