Custom board with STM32L476ZG - first steps?

Mbed OS Hello world!
1

Hi everyone,

I am rather new to Mbed and STM32 programming in general. I am looking for a way to create a target for a custom board with an STM32L476ZG. Is there an “easy” way to do this? As far as I see, there currently is no board available with an STM32L476ZG, which I could use and remap, right?

Thanks in advance!

2

Hello,

I have no persotal experince with this, but on the page 15 of Datasheet - STM32L476xx you can found some differentions between STM32L476ZG and STM32L476RG what is used on NUCLEO-L476RG | Mbed.
Maybe that can be used as a start point.

README for Mbed OS STM32 targets - custom-boards

BR, Jan

3

Hi,

As far as I see, there currently is no board available with an STM32L476ZG, which I could use and remap, right?

Correct. There is no STM32L476ZG support, but STM32L476xG is available, so you can re-use the code.

Build step

  • Clone mbed-os-example-blinky project
  • Copy one of target board related folder to the root. e.g.
  • And rename it for you custom board. e.g. TARGET_MY_L476ZG
  • Create custom_targets.json and add your board config below:
{
    "MY_L476ZG": {
        "inherits": [
            "MCU_STM32L476xG"
        ]
    }
}
  • Modify linker script files and pinmap files in the folder

Also, you can refer my custom board project here:

I hope this helps.

4

Thanks a lot for your responses! I tried to add a custom target with the following steps:

  1. Created the blinky example: mbed import mbed-os-example-blinky
  2. Created a custom_targets.json with the following content:
{
    "WOMOLIN_V2": {
        "inherits": [
            "MCU_STM32L476xG"
        ]
    }
}
  1. Generated the pin mapping files following the link to the README posted by @JohnnyK :
    Inside mbed-os-example-blinky 
cd mbed-os
python targets/TARGET_STM/tools/STM32_gen_PeripheralPins.py -m "STM32L476Z(E-G)Tx.xml"
  1. Copied PeripheralPins.c and PinNames.h from mbed-os/targets_custom/TARGET_STM/TARGET_STM32L4/TARGET_STM32L476xG/TARGET_STM32L476ZGT to a new folder TARGET_WOMOLIN_V2 inside mbed-os-example-blinky
  2. Changed the content of PinNames.h to match my configuration (see here)
  3. Compiled the code with mbed compile -m WOMOLIN_V2 -t GCC_ARM

Am I on the right track so far?

I noticed a warning when compiling:

Configuration error: Bootloader not supported on this target. ROM start not found in targets.json.
Configuration error: Bootloader not supported on this target. RAM start not found in targets.json.

As far as I understand, the ROM and RAM start should be defined in the target.json, which I am extending with my custom_targets.json. I would expect the inherits to take the values for the RAM and ROM start from the already defined parent definition MCU_STM32L476xG. Any ideas what is happening here? How can I fix that?

I set the STM32 into bootloader mode by pressing the boot button on the board and connecting it to USB. lsusb lists it as Bus 001 Device 018: ID 0483:3748 STMicroelectronics ST-LINK/V2. When executing mbed compile -m WOMOLIN_V2 -t GCC_ARM -f to flash the code, I get

[1614191038.26][mbedls.lstools_linux]Could not get serial devices by id. This could be because your Linux distribution does not use udev, or does not create /dev/serial/by-id symlinks. Please submit an issue to github.com/armmbed/mbed-ls.

I think this may be my setup of mbed (installed via aur on Arch Linux).

I also tried flashing the firmware using Mbed Studio. When connecting the board in bootloader mode, it does show up as STM32 BOOTLOADER. I added the configuration as you can see in the screenshot here:
Bildschirmfoto von 2021-02-24 19-53-08
When clicking “Run program”, Mbed seems to be stuck. Checking running processes, I noticed pyocd flash running in the background, but it won’t finish. Clicking “Debug program” quits with a timeout: “Timeout waiting for gdb server”
Is it possible to get Mbed Studio to flash my program or should I stick with flashing via my STLinkV2?

Thank you very much for your answers!

5

Hi,

The build tool refers target ROM and RAM start address from CMSIS package file which is in mbed-os/tools/arm_package_manager/index.json.
Your target device is configured as STM32L476ZGTx in the file, so you can modify your custom_targets.json as below.

{
    "WOMOLIN_V2": {
        "inherits": [
            "MCU_STM32L476xG"
        ],
        "device_name": "STM32L476ZGTx"
    }
}

Thanks,
Toyo

6

Thanks! The error is gone :slight_smile:

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