Backward compatibility

[GauravK]

Hi, for our development we have selected "STM32F207ZG". The eval board which I see for MCU is "NUCLEO-F207ZG", which has pin-outs but not the required hardware interfaces on-board (usb-c fs, micro-sd, lcd, fsmc).

The dev board "32F469IDISCOVERY" has some on-board interfaces but based on M4.

Questions:

1. Can M4 program be directly reused for M3. Any changes in compilation, as M4 has DSP hardware?

2. Suggestions for dev board for above requirement.

3. Does FreeRTOS have support for M3, M4 and necessary interfaces

4. Can the interfaces be done without FreeRTOS libraries.

Request to look into above queries.

[FBL]

Hello @GauravK 

About reusing your software for CM3, you need to consider some points:

• DSP instruction and floating point operations are no supported on CM3
• Peripheral specifications should be checked for any differences between your microcontrollers 

For future design, it is recommended to use new MCUs to take advantage of latest improvements. Also, consider long term availability and support for the MCU.

About your last 2 questions, implementing RTOS in general is not a requirement for interfacing with hardware peripherals. It depends on your application. FreeRTOS provides kernel support. To handle peripheral drivers, you should use latest Cube firmware on GitHub which includes necessary drivers and APIs.

[Andrew Neil]

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@GauravK wrote:

"NUCLEO-F207ZG", which has pin-outs but not the required hardware interfaces on-boards.

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So add the required hardware off the board, then ?

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@GauravK wrote:

1. Can M4 program be directly reused for M3. Any changes in compilation, as M4 has DSP hardware?

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It will, at the very least, require re-compilation.

(Almost) certainly, there will be differences that will require source code changes.

As @FBL said, you will need a detailed check of the documentation (Datasheet & Reference Manual) for each to chip to find what's compatible, and what's not.

[GauravK]

Thanks, FBL and Andrew for quick responses. More questions:

1. Dev boards have USB micro AB FS support.

    a. Can I know board available with USB Hi speed.

    b. What changes in drivers for USB micro AB to USB-C

[Tesla DeLorean]

Most don't have USB-HS, there might be a few of the EVAL series board.

The STM32F723 has a built in HS PHY

Perhaps look at STM32F723E-DISCO

https://www.st.com/en/evaluation-tools/32f723ediscovery.html

[GauravK]

If a external memory parallel interface is shared by MCU and another device, can DMA be used as slave here. Pl guide

[Tesla DeLorean · Accepted solution]

The FMC bus can use DMA in a Memory-to-Memory mode, F2/F4 that would need to be DMA2 resource.

Perhaps look at other boards entirely. A lot of the newer DISCO boards have MicroSD, SDRAM and LCD

Perhaps look at WaveShare boards, or the many many examples on AliExpress, Taobao, etc.

>> Pl guide

Read Manuals, review board schematics, make a check list of the items you want/need

[GauravK]

Can I know memory requirements for flash and RAM for interfaces and OS

I found, freeRTOS >64 kB RAM, 128 kB flash

sd card: ~3 kB

Pl can I know above are ok and memory for DMA, USB, FSMC, LCD and its respective library uses. 

[GauravK]

Looks Im not getting further replies...  I will close this post and open new when needed

[Andrew Neil]

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@GauravK wrote:

Can I know memory requirements for flash and RAM for interfaces and OS

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That question is way too vague to answer.

But it's a whole new question from the original "Backward compatibility" of STM32F2 and F4.

Suggest you mark a solution for the "Backward compatibility" question in this thread, and start a new thread for the new question - with more detail for people to go on.

Post a link here to the new thread.