Cypress FX3 USB microcontroller has an integrated boot loader, which starts automatically after power-up or reset and when no valid firmware is present in the FLASH memory.
For USB microcontroller firmware upgrade, please use the “CyControl.exe” application from cy_ssusbsuite_v1.3.3.zip package.
If FLASH memory is empty or connector J17 (on LimeSDR-USB board) is open, USB3 microcontroller boots-up into bootloader mode. Cypress drivers from cy_ssusbsuite_v1.3.3.zip package must be installed first. Download the package here. Run the “USB Control Center” application and select Cypress USB BootLoader line as shown in Figure 5.