https://bugzilla.kernel.org/show_bug.cgi?id=210351 Bug ID: 210351 Summary: Wrong setting baudrate for FTDI chip FT230X Product: Drivers Version: 2.5 Kernel Version: all Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: USB Assignee: drivers_usb@xxxxxxxxxxxxxxxxxxxxxx Reporter: svv75@xxxxxxx Regression: No Hello! I have three chips FT232BL, FT232R and FT230X. I am using them as a VCP on Linux (Ubuntu 18.04). According to Application Note AN_120 from FTDI, the baud rate generators of all these chips have 8 sub-integer prescalers. Divisor = 3000000 / baudrate = n + 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875. Where n is an integer between 2 and16384. So, I measured real baud rates, for n = 2 in combination with all possible sub-integer prescalers. And it turned out that all sub-integer prescalers worked for FT232BL, FT232R chips. And for the FT230X, only a few prescalers work correctly. The following shows exactly how prescalers behave: 0 - correct 0.125 - correct 0.25 - correct 0.375 - WRONG! (works like 0.125) 0.5 - correct 0.625 - WRONG! (works like 0.5) 0.75 - WRONG! (works like 0.25) 0.875 - WRONG! (works like 0.125) The same for the other n. I think it is a driver problem, it initializes the sub-integer prescaler incorrectly. Since under Windows FT230X works fine with all sub-integer prescalers. -- You are receiving this mail because: You are watching the assignee of the bug.
