I’m too impatient for Dallas Semi to send samples of the DS2408 so I implemented a switch using the parallel port on my FreeBSD server.<\/p>\n
The idea is to use the DS2408 or parallel port to drive a relay to switch the HVAC “call for heat” line. This way I can cron my heating schedule.<\/p>\n
Brian and Smart-Works were nice enough to loan me two temperature sensors and some space on their web server for the temperature log.<\/p>\n
I thought I would be able to echo 1 > \/dev\/lpt0. Ha. No…<\/p>\n
FreeBSD includes the ability to use the “geek” port. I wish I were making that up, but that’s what `man ppi` says. FreeBSD uses ioctl to access the parallel port interface. Here’s the sample from the ppi man page:<\/p>\n
#include stdio .h
\n#include dev\/ppbus\/ppi.h
\n#include dev\/ppbus\/ppbconf.h
\n#include fcntl .h
\n\/\/The includes above need less than greater than brackets.<\/p>\n
int main (void)
\n{
\n int fd;
\n u_int8_t val;<\/p>\n
fd = open (“\/dev\/ppi0”, O_RDWR);
\n val = 0x1;<\/p>\n
ioctl (fd, PPISDATA, &val);
\n ioctl (fd, PPIGCTRL, &val);
\n val |= STROBE;
\n ioctl (fd, PPISCTRL, &val);
\n val &= ~STROBE;
\n ioctl (fd, PPISCTRL, &val);
\n}<\/p>\n
I’m actually going to use some logic so that I can use more than eight devices connected to the parallel port.<\/p>\n","protected":false},"excerpt":{"rendered":"