• Author Author: rscasny
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Need Help in Selecting an MCU Board for a Roadtest

rscasny

Several weeks ago, I asked for your help in selecting a motor of a roadtest. Here's the blog: Seeking Assistance in Selecting a Motor for a Single-Phase Inverter Roadtest

 

With your input and help, I went back to the sponsor and we selected a motor.

 

So, here is what each roadtester will receive:

 

one Fan motor

https://www.yoycart.com/Product/567509041351/  (The sponsor selected this)

 

one RDK-872 - Reference Design Kit for BridgeSwitch (70 W Single-Phase Inverter Using BridgeSwitch for Fan Application)

https://www.power.com/design-support/design-kits/rdk-872-reference-design-kit

 

one RDK-873 - Reference Design Kit for BridgeSwitch (30 W Single-Phase Inverter Using BridgeSwitch Motor Driver)

https://www.power.com/design-support/design-kits/rdk-873-reference-design-kit

 

The motor drivers need an MCU board.

 

The sponsor gave me some recommendations for MCU boards. Here's what they said:

 

"Preferred MCU core is CortexM0. A good reference with minimum MCU resources below. One would need these resources not only to run the MC SW but also implement some debugging capabilities with FAULT, communication to PC, etc. Its better to start bigger on resources. The 1-phase SW examples on our website run on CortexM0 from IFX and are in DAVE. One can take the SW and port it to IAR where there is support for both NXP and Renesas."

 

 

Feature

Minimum Requirement 1-phase BLDC

Description

MCU Core

CortexM0/M0+

Flash / SRAM (KBytes)

20 KB /8KB

For application development larger memory capacity is needed

Execution Performance (MIPS)

32MIPS

Performance requirements also includes CPU clock frequency, latency of Flash and SRAM

Timers

1 (96MHz clock)

Critical in generating PWM clock with at least 20KHz carrier frequency and 11 bit of resolution. Faster timer clock delivers higher PWM resolution = better precision and controller performance.

ADC

12-bit / 11 ENOB* @1Msps, 4-6 channels

# of ch. should allow the scanning of current / voltage as needed by the chosen control algorithms.

Analog Comparators

3 channels, 100ns response time

Needed for proper operation of the zero-cross detection when operating in trapezoidal commutation mode

Bridge Switch FAULT

2 x GPIO

Bi-directional GPIO (open drain)

JTAG or SWD

Debug interface

Required for debugging purpose

GPIOs

Min 6 inputs, 4 outputs

Sampling of the HALL sensor state. Alternative as command interface to the UART and the Host.

UART - Communication

Min 115.2Kbps

The UART interface is required for host communication

 

I'd like to get a recommendation of an MCU board for this roadtest. The sponsor mentions both NXP and Renesas. But I am open to other possibilities such as Infineon or other manufacturer.

 

I'd appreciate any suggestions in the comments section below. Thanks.

 

Randall Scasny

RoadTest Program Manager

  • Back in 2018, I have roadtested Infineon XMC 1100. Looking at the table and recommended MCU specification, I could suggest this one.

     

    http://www.farnell.com/datasheets/2059677.pdf

     

    But, as you have already decided, RPI-Pico, that is also impressive.

  • I wanted to report back to you as soon as I heard back from the sponsor. I took your ideas and suggestions to the sponsor to get their feedback.

    Their preference is the Raspberry Pi Pico.

     

    Now, the focus on the roadtest is the 2 driver boards they make (BridgeSwitch). One is a 30W and the other is 70W.

     

    But we are throwing in a Fan motor. Actually an entire floor fan. I have one right next to me desk in our office and its a decent size.

     

    And of course, the Pi Pico will be included in the roadtest kit.

     

    I am hoping to launch this roadtest this week.

     

    Thanks.

     

    Randall Scasny

    RoadTest Program Manager

  • in reply to misaz

    Good work checking into MCUs.

    Another one is LPC51U68 which runs at 150 MHz

    There are some dual core CortexM4/M0 MCUs where the M0 core runs over 96 MHz as well, such as PSoC6.

  • in reply to dougw

    I did not say that they does not exists at all, but I said that very few Cortex-M0 MCUs support running so fast. I researched over all vendors which I know and all their CM0 or CM0+ MCUs and I found that following does not comply with 96 MHz clock requirement.

    image

    Of course some high performance CM0 exists and RP2040 is not the only one supporting this. All CM0 MCUs which comply with requirement are:

    image

     

    As you can see list is much shorter than list of MCU which does not comply so I think my statement that most CM0 MCUs does not comply was correct. Note that I research only vendors which I know and only MCU with listed parameters publicly. There are probably plenty CM0 MCUs which I dont know. Also note that requirement mention PWM input clock but there are some MCU which have peripherals clocked on lower or higher frequencies than CPU core. It is example of Nuvton M0564 which can clock peripherals at 144 MHz max but Cortex-M0 core can be clocked only at half of this frequency (72 MHz max).

  • in reply to dougw

    Indeed so. I wondered about the ADC requirement (11 ENOB* @1Msps, 4-6 channels - # of ch. should allow the scanning of current / voltage as needed by the chosen control algorithms) and the Analog Comparator requirement (3 channels, 100ns response time - Needed for proper operation of the zero-cross detection when operating in trapezoidal commutation mode). The Pico's PIO could be useful though.