I tried to rewrite the D300 MCU firmware update work in an easy-to-understand manner.
Prepare for update
Unzip the downloaded update file "SMSL D300_MCU_FW 221012".
”IAP_D300_MM32_1v1.hex” in the unzipped folder ”SMSL D300_MCU_FW 221012” is the configuration file to be specified in the update work.
Furthermore, unzip "ISP_PC_EN.zip" in the folder.
"ispV2.4.exe" in the unzipped folder is the update tool.
Turn off the power switch on the back of the D300 before starting the update process.
Remove the USB cable connecting the D300 and the PC.
Click "ispV2.4.exe" to launch the update tool.
Click "File" in the upper left corner of the screen, then click "Open".
On the screen to specify the installation file, specify "IAP_D300_MM32_1v1.hex" in the unzipped folder and click "Open" at the bottom right.
Wait 30 seconds for the update tool to prepare the files for deployment. At this time, there is no change on the PC screen.
After 30 seconds, connect D300 and PC with USB cable.
Hold down the FN button and turn on the power switch on the back of the D300. Release the FN button after 5 seconds.
At this time, the screen of D300 remains off and there is no change.
"Disconnect" is displayed at the bottom left of the PC screen.
If the D300 normal screen is displayed by this operation, redo the operation.
After 30 seconds have passed, click the "handshake icon" in the upper right corner of the PC screen.
Then "Disconnect" at the bottom left of the screen will change to "Connect".
Click “Start Program” displayed near the center left of the screen.
The firmware update process will begin and you will see flowing text on the right side of the screen indicating the processing steps.
When the update is finished, "Complete" is displayed and the screen of D300 lights up and it becomes normal operation.
This completes the update work.