ok but what is so different between Cypress and the others ?
My chip is well enumerated as virtual COM port and time to time i can recovery my board without any errors.
as soon it is enumerated in windows, normally it becomes a standard uart interface and it is more or less silicon supplier independant, no ?
thanks for clarification.
Have you checked the logic level voltages between the BCM and the USB serial device? Table 13 in the Module technical reference describes the logic levels expected by the BCM. Make sure your logic levels are matched.
I built a programming cable using an FTDI 3.3V USB UART device. When the cable was 4 feet long it did not work. When I shortened it to one foot long it works every time now.