Introduction

One of the biggest issues with MSXI's electrical system was its inconsistency in parts and pinouts. There were at least 3 variations of the CAN controller/transceiver circuit and which SPI bus they were connected to, making debugging difficult. Some used different footprints, while others used different parts. This also made inventory a challenge, as each board had its own very specific set of components.

To increase board consistency and ease debugging, we propose a controller board that consists of shared core components such as the microcontroller, CAN transceiver, and possibly some debug LEDs or IOs. These controller boards would likely use a mezzanine connector to allow breakouts to carrier boards, which should be much simpler.

Key Features

• Allows creation of a debug carrier board to allow self-test of the MCU and CAN
• CAN lines are directly routed through the board, reducing the use of T-junctions
• Includes CAN, USB 2.0, SPI, UART protocols
• Simplifies inventory management and software, allowing a single core config for all boards
• Simplifies board debugging - isolates issues to either the controller or carrier boards
• Reduces cost of bringing up backup boards
• Debug/Heartbeat LEDs and programming header

Things To Consider

• UART/USB? If we use USB, may need serial-to-usb converters on-board (In-car debugging)
• Daisy-chaining power or not (LV Power granularity)
• Hermaphroditic or not (Cost)
• Switching regulator circuit or integrated DC-DC converter (board complexity, cost)
• LQFP vs UFQFPN
• How many pins do we dedicate to 3.3V, 12V, and GND on the mezzanine?

Part Selection

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ARM Cortex-M0

Includes CAN controller, 37 IOs, 48-LQFP

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497-14645-ND

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TCAN332DR

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CAN Transceiver

Replacement for the SN65HVD232DR

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296-43711-1-ND

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1.25mm pitch for signal, 1.5mm pitch for power

Off-board connectors used for CAN, power, etc.

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MCU Schematic Capture

Peripheral Selection

• 51 GPIOs
• 2 SPI, 2 I2C, 4 USART, CAN, USB, HDMI-CEC
• 16 Channel 12-bit ADC
• 18 Capacitive Sense Channels
• 2 Analog Comparators
• Serial Wire Debug (SWD)

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