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
| MFG Part # | Info | Digikey Link | Product Details |
|---|---|---|---|
STM32F072RBT6 | ARM Cortex-M0 microcontroller 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 |
| |
| ??? | CAN connector TODO: Move to different connector for internal CAN connections? | ||
TE 1565357-6 | 50 pin, 0.5mm pitch, 4-6mm stack height Non-hermaphroditic but slightly cheaper | A110996CT-ND | http://www.te.com/usa-en/product-1565357-6.html#pdp-docs-features
|
10106813-051112LF | Mezzostak Hermaphroditic connectors Samples have been requested | 609-4602-1-ND | |
LS2-125-01-F-D-RA1 | Samtec LS2 locking hermaphroditic connectors SICK SHIT, but they keep getting sold out on digikey and are a bit more expensive Samples have been requested | LS2-125-01-F-D-RA1-ND |
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).