Someone may encounter the ezspForceReset error during launching the host application. the most common cause of this issue is uart or spi communication failure.here are some suggestions for debugging this issue.
1. To make sure uart/spi work properly on the host part.
2. To make sure the ncp firmware works properly.
here is a simple way to indentify whether the ncp firmware works properly.
If there is no log printed when you reset the ncp. that means the ncp doesn't work properly.In this case, it is recommended to use pre-build ncp image to exclude the firmware issue. if the pre-build ncp image for your part number can't be found in ncp-images folder. You can only build the customized ncp image by reference to https://www.silabs.com/documents/public/application-notes/an1010-customized-ncp.pdf
3. If the host application still can't be launched successfully, you have to capture the waveform from the uart or spi pins with logic analyzer or oscilloscope, and then compare the waveform with the expected one which described in https://www.silabs.com/documents/public/application-notes/an711-ezsp-spi-host-interfacing-guide.pdf or https://www.silabs.com/documents/public/application-notes/an706-ezsp-uart-host-interfacing-guide.pdf
As confirmed by Haoyang.
If you still have an error trying to open the serial port with cygwin in windows. Check the following, it works for me.
It doesn't seem like that Cygwin supports COM port number as high as 77. You can issue the command "ls /dev/" in Cygwin terminal to see all the com driver file. When I have the COM port number of my NCP as 77, the corresponding "ttyS76" is not shown under "/dev/" and if I run the host application, I will get the same error that you got.
However, if I change the COM port number in Windows -> Device Manager -> JLink CDC UART Port (COM77) -> Properties -> Port Settings -> Advanced -> COM Port Number to, for example, one of the non-used port 10, the NCP works just fine with "./Z3GatewayHost.exe -n 0 -p COM10". Can you try to change the COM Port Number and see how it goes?