On Thu, Jan 07, 2021 at 03:06:07PM -0600, Joe Abbott wrote: > Got redirected here by GKH email-bot. > > My message to him was: > I have an ASR33 teletype that I'm trying to communicate with using a > PL2303 based Benfei USB serial adapter. The ASR requires 110 baud 7E1 > and it appears that the driver is defaulting to 9600 baud. (possibly > because the baud_sup array doesn't contain 110?) I've tried adding > 110 to the array and recompiling but that doesn't seem to help. I did > have to comment out the '/ SPDX-License-Identifier: GPL-2.0' line in > pl2303.c to get it to compile. No, you don't need to add 110 to the baud_sup array as 110 baud is set using divisors (i.e. pl2303_encode_baud_rate_divisor()). > The windows driver works so the hardware is capable. > > I must be missing something. Any help appreciated. > > Running Mint 19.3 64-bit. > > I'm using stty to set baud rate like this: > stty 110 cs7 evenp -F /dev/ttyUSB0 > stty reports that 110 is in use when I: > stty -F /dev/ttyUSB0 > > Oscope shows 150 and above changing (didn't try 75) but 110 reverts to > 9600 (mentioned in pl2303.c file). I just verified using a logic analyser that 110 baud works just fine here (with even parity too) using a PL2303 HXD. Not sure what kernel version you're on, but this should have been supported since at least around 2015 (and I think we backported the corresponding fix of the divisor algorithm to earlier kernels). Try a recent mainline kernel or enable dynamic debugging and make sure the line request is sent correctly (110 cs7 parenb): pl2303_set_line_request - d5 0e 00 80 00 02 07 If there's some difference in how your device encodes baud rates you may be able to compare that with what the Windows driver uses by tracing the USB packets. Johan
