Picomod7 custom serial baud rate

RSchubert · May 21st 2012

Is there a way to set a custom serial baud rate on COM1 (/dev/ttySAC1) on Picomod7 ?

What I tried:

Code

struct serial_struct new_serdrvinfo;
ioctl(fd, TIOCGSERIAL, &new_serdrvinfo); // read driver settings
new_serdrvinfo.flags = (new_serdrvinfo.flags & ~ASYNC_SPD_MASK) | ASYNC_SPD_CUST; // activate custom baudrate
printf("BaudBase: %i - Divisor: %i\n",new_serdrvinfo.baud_base,new_serdrvinfo.custom_divisor);
// new_serdrvinfo.baud_base=3000000;
// new_serdrvinfo.custom_divisor = 6; // set custom divisor
ioctl(fd, TIOCSSERIAL, &new_serdrvinfo); // write new driver settings

The baud_base and custom_divisor parameters both are zero. When I try to set some values the ioctl(fd, TIOSSERIAL, xxx) blocks or the hole program hangs up.

Calling #setserial -a /dev/ttySAC1 returns zero for the two parameters also. The UART IC is "undefined" and Port ist returned as 0x0000.

It's possible to use some additional defined values like B460800 or B500000 (they are working) but I need 520000.

Any idea? Thanks.

fs-support_DK · May 21st 2012

Could you pls try this:

Code

struct termios options;
tcgetattr(fd, &options);
cfsetispeed(&options, B38400);
cfsetospeed(&options, B38400);
options.c_cflag |= (CLOCAL | CREAD);
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;
tcsetattr(fd, TCSANOW, &options);

RSchubert · May 21st 2012

this already was in the code:

Code

tcgetattr(fd,&oldtio); /* save current port settings */
newtio.c_cflag = B38400 | CS8 | CLOCAL | CREAD;
newtio.c_iflag = IXANY;
newtio.c_oflag = 0;
newtio.c_lflag = 0;
newtio.c_cc[VMIN]=1;
newtio.c_cc[VTIME]=0;
tcsetattr(fd,TCSANOW,&newtio);

I also tried your piece of code. The result is the same. Baud_base and divisor are 0 and writing the values causes crashing the serial driver (I have to reboot to get the serial port working again). Maybe the problem ist, that there's no known serial driver (see setserial output)??

fs-support_DK · Jun 1st 2012

that code works for PicoMOD7

Code

int initport(int fd, int speed) {
struct termios options;
// Get the current options for the port...
tcgetattr(fd, &options);
switch(speed) {
case 0: speed = B0; break;
case 50: speed = B50; break;
case 110: speed = B110; break;
case 134: speed = B134; break;
case 150: speed = B150; break;
case 200: speed = B200; break;
case 300: speed = B300; break;
case 600: speed = B600; break;
case 1200: speed = B1200; break;
case 1800: speed = B1800; break;
case 2400: speed = B2400; break;
case 4800: speed = B4800; break;
case 9600: speed = B9600; break;
case 19200: speed = B19200; break;
case 38400: speed = B38400; break;
case 57600: speed = B57600; break;
}
cfsetispeed(&options, /*B38400*/speed);
cfsetospeed(&options, /*B38400*/speed);
// Enable the receiver and set local mode...
options.c_cflag |= (CLOCAL | CREAD);
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;
// Set the new options for the port...
tcsetattr(fd, TCSANOW, &options);
return 1;
}

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RSchubert · Jun 4th 2012

Setting one of the default bitrates defined by Bxxxxx is working. My problem is that I need a custom baudrate (520000 baud) because of communication with a slow CPU where I cannot divide the clock to a fast default value.

Any ideas? Thanks.

RSchubert · Aug 31st 2012

any news about the serial driver? In Kernel version 0.2 custom baud rates are not supported.

Kind regards
RSchubert

fs-support_DK · Sep 3rd 2012

What a baud rate do you need to setup?

RSchubert · Sep 3rd 2012

520000 would be the best rate. The cause is that I'm using a slow CPU on the other end of the serial connection that runs with only 40 MHz. On this slow CPU the clock divisor is verly low (2 or 3) on this high baud rate - so I'ts not possible to fit any standard value. Even at 115200 baud rate the clock error is about 3%.

RSchubert · Sep 10th 2012

It's working with a Kernel patch from F&S.

Thanks

fs-support_HK · Sep 10th 2012

A short check of the sources showed that you have to set the speed to B38400 if you want to use a custom divider. The Samsung serial driver does not set the baud_base correctly, so you can not use this value. I'm not 100% sure right now but I would expect the base clock to be 66.7MHz, so your divider should be something about 128 to get 520000. Using low values as 6 might result in a too high serial speed so that this causes the complete board to hang.

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