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
- 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
Part Selection
| Info | Digikey Link | Product Details | Image |
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ARM Cortex-M0 microcontroller STM32F072RBT6 Includes CAN controller, 51 IOs, 64-LQFP | 497-14644-ND | http://www.st.com/content/st_com/en/products/microcontrollers/stm32-32-bit-arm-cortex-mcus/stm32f0-series/stm32f0x2/stm32f072rb.html | |
TCAN332DR CAN Transceiver Replacement for the SN65HVD232DR |
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External CAN connector | |||
Molex internal wire-to-board surface mount PCB headers Molex internal wire-to-board connector housings Molex internal wire-to-board connector crimp terminals |
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Molex internal wire-to-board surface mount PCB headers Molex internal wire-to-board connector housings Molex internal wire-to-board connector crimp terminals | http://www.molex.com/molex/products/datasheet.jsp?part=active/0039014050_CRIMP_HOUSINGS.xml Mini-Fit Jr |
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TE internal wire-to-board through hole PCB headers TE internal wire-to-board surface mount PCB headers TE internal wire-to-board flat flex cable assembly | AMPMODU MTE |
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TE internal wire-to-board surface mount PCB headers TE internal wire-to-board connector housings TE internal wire-to-board connector crimp terminals | Low-profile Micro Mate-N-Lok |
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Board-to-board IO terminal Non-hermaphroditic but slightly cheaper | A110996CT-ND | http://www.te.com/usa-en/product-1565357-6.html#pdp-docs-features
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Board-to-board IO terminal Mezzostak Hermaphroditic connectors Samples from FCI are out of stock, order from Digikey | 609-4602-1-ND |
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Board-to-board IO terminal Samtec LS2 locking hermaphroditic connectors Samples have been requested Electrical and mechanical models available | LS2-125-01-F-D-RA1-ND |
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Board-to-board IO terminal Samtec LSHM high-speed hermaphroditic terminals Samples have been requested Electrical and mechanical models available | Not on Digikey, will have to find supplier LSHM-150-02.5-L-DV-A-S-TR |
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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)
Most I/O pins on the STM32F072 are also used for peripheral functions such as SPI, I2C, USART, CAN, USB, CEC, SWD, etc. To increase flexibility, most of the I/O will be routed to the carrier board. Since the peripherals and I/O pins are muxed internally, the controller board can provide either function to the carrier board without special requirements.
Important notes
- PC13, PC14 and PC15 are supplied through the power switch. Since the switch only sinks a limited amount of current (3 mA), the use of GPIOs PC13 to PC15 in output mode is limited: The speed should not exceed 2 MHz with a maximum load of 30 pF. These GPIOs must not be used as current sources (e.g. to drive an LED).