Establishing serial communication over UART instead of USB in MAX25405 EVKIT

Hi, today I tried flash the firmware to the device and my physical UART interface work when compiled with MBED OS checked to revision 0fdfcf7350896a9c0b57c4a18237677abfe25f1a and USE_UART_INTERFACE set to 1. AT least it respond to ver command. As of now I did not tried advanced commands yet. UART is on pins P3.0 and P3.1 exactly as you have connected. For sure I am attaching my build of firmware: https://misaz.cz/Public/files/max25405fw_real_uart.bin

But, I had issues with flashing firmware to the device using bootloader. In my case after draging new firmware and waiting bootloader rebooted but FAIL.TXT file occured with description that flashing failed with error "The transfer timed out". I tired copy file from WIndows machine and also from Linux (Raspberry Pi) but in both case I received this error. Are you sure that you flashed firmware successfuly? After flashing firmware and reseting FTHR board "Maxim Serial Port" should dsiappear from Windows Device Manager. If you see Maxim Serial Port after "flashing", than your flashing procedure were unsuccessfull and your MCU still runs old (stock) firmware.

Because I was unsuccessfull with bootloader then I used alternative way - JTAG probe. I flashed firmware to the MAX32620 MCU using PICO adapter and openocd with following command:

"C:\Maxim\Toolchain\bin\openocd.exe" -s C:\Maxim\Toolchain\share\openocd\scripts -f interface/cmsis-dap.cfg -f target/max32620.cfg -c "init" -c "halt" -c "program D:/path/to/max25405fw_real_uart.bin verify"

But this approach of course requires JTAG probe.

For sure I am posting photo of my setup. I use FTHR board on breadboard. Here I connected CP2102 USB-to-UART converter connected to pins P3.1 and P3.0 of FTHR board and I also used logic analyzer to check UART signals. Last board is MAX32625PICO board which I used with debugging:

Then I was able to connect to open CP2102 COM port in Putty and execute some commands. Note that firmware has no echo feature, so typed commands are not visible and I had to enter Ctrl + J to send \n (by default putty sends \r on enter). But after sending commands I successfully received replies from firmware:

ver
reg read 0 6

Thanks! This actually helped. After flashing the firmware, I was not waiting long enough, I was thinking the firmware file is very small and as soon as I copy paste I was manually resetting the controller. However today after copying the binary, I waited for the MCU to reset and I got the fail file. Timeout error.

I do not have PICO board for debugging nor do I have JTAG probe. I have a STM32 Nucleo board with STlink pcb. It has JTAG interface. I'm not sure if I can use that one.

Otherwise I'll just purchase a new JTAG probe.

EDIT: Can I use the MAX32625PICO board for programming the MAX32620FTHR board? Or I have to buy JTAG probe separately?

Thanks! This actually helped. After flashing the firmware, I was not waiting long enough, I was thinking the firmware file is very small and as soon as I copy paste I was manually resetting the controller. However today after copying the binary, I waited for the MCU to reset and I got the fail file. Timeout error.

I do not have PICO board for debugging nor do I have JTAG probe. I have a STM32 Nucleo board with STlink pcb. It has JTAG interface. I'm not sure if I can use that one.

Otherwise I'll just purchase a new JTAG probe.

EDIT: Can I use the MAX32625PICO board for programming the MAX32620FTHR board? Or I have to buy JTAG probe separately?

Mbed uses Arm Mbed DAPLink. To check if there is suitable firmware use https://daplink.io/

Another consideration, if you had the Arduino bootloader installed (i.e. if you plug in the USB cable into the board and the computer and a folder pops up on your computer screen then you have a bootloader installed), is to make allowances for the bootloader inside Mbed Studio. This is a setting applied during compile so that it does not try and override the bootloader memory. It will usually fail because of this.

On a Linux computer you can see the bootloader used at: .arduino15/packages/Maxim/tools/daplink/1.0.2/bootloader

You can see that a "mount point" is used in the Arduino platform.txt file for the MAX32620FTHR board: tools.daplink.upload.mountPoint=BOOTLOADER

When you use the Native USB Port option in Arduino to flash firmware onto the MAX32620FTHR it uses compiler options in the boards.txt file.

max32620_fthr_bl.build.extra_flags=-mthumb -D__SYSTEM_HFX=96000000 -DTARGET=MAX32620 -DTARGET_REV=0x4332 -DUSBCON -DMAX32620 -DMAX32620FTHR_BOOTLOADER -DARDUINO_MAXIM

Then you have to hunt for it, as it's buried... is the linker script file (max32620_bl.ld). Here it gives us what we want to know:

MEMORY {
    FLASH (rx) : ORIGIN = 0x00010000, LENGTH = 2M - 64K /* start from 0x0, allowing bootloader */
    SRAM (rwx) : ORIGIN = 0x20000000, LENGTH = 256K     /* full-size SRAM, 256K */
}

Then in Mbed you'll need to adjust the targets.json file or make a mod in mbed_app.json to show a change in the ROM start position as well as size.

Hi thanks for the detailed explanation, but I have not flashed arduino bootloader in the MAX32620. It is the original bootloader from Maxim only. 

yes, it is more likely than not one and the same, as it originates from Maxim.

I just burned the bootloader onto the board using the Arduino IDE. I get two folders. One is DAPLink and the other is Bootloader... you would also get the Bootloader folder by holding down the boot button when powering the board.

Do you have the same?

I just tested by using the following mbed_app.json file and it works - I could drag and drop the compiled bin file and it did not time out:

I get the bootloader drive when I hold the boot button while powering it up. But when I drag and drop a binary file into the bootloader file, it says timeout error

This is my details text file inside the bootloader drive

It's pretty much the same... key is bootloader version

# DAPLink Firmware - see https://mbed.com/daplink
Unique ID: 000000009ecfc04000000000000000000000000097969904
HIC ID: 97969904
Auto Reset: 0
Automation allowed: 1
Daplink Mode: Bootloader
Bootloader Version: 0242
Git SHA: 33e3ba1b4a53f190d35bd40421a6c67f9c1842a2
Local Mods: 1
USB Interfaces: MSD
Interface CRC: 0xbb0e972e

Hi. After yet another experiments and some hints from BigG I successfully found the cause of the issue.

It looks that DAPLINK checks for binary data and most probably checks some data in binary (I gues it checks for vector table). The reason is that by default our firmware is compiled with addresses starting at zero which are used for DAPLINK firmware. You need to recompile with address skipping bootloader. Change contents of mbed_app.json file to following:

{
	"target_overrides": {
		"*": {
			"target.mbed_rom_start": "0x00010000",
			"target.mbed_rom_size": "0x001F0000"
		}
	},
    "config": {
        "main-stack-size": {
            "value": 65536
        }
    }
}

Then open mbed-os/targets/TARGET_Maxim/TARGET_MAX32620C/device/TOOLCHAIN_GCC_ARM/max32620.ld file and update line #36 containing FLASH memory definition to following:

FLASH (rx) : ORIGIN = 0x00010000, LENGTH = 2031616

This change linker script for TARGET_MAX32620C (note the C at the end). I am not sure why my MBED environment selected target ending with C but I recommend change this line in both TARGET directories.

After that you get firmware which you will be able to flash to the device.

Thanks. I will try it. I'm using the online mbed compiler so will have to look for those files in mbed-os. Thank you BigG and misaz

for helping me

it seems that this feature is not supported in online compiler. Will have to try in CLI on windows