Copyright (c) 2001 THOMSON multimedia Using the idtdisplay character device with Linux ------------------------------------------------ Contents: 1) Overview 2) How to use the display ? 3) Module Command Line Parameters 4) An example using idtDisplay 5) Run and Stop the driver 6) Generate thecnical documentation with doxygen 1) Overview ----------- Idtdisplay is a driver wich allows one to display 4 characters on a digital display, mounted on an IDT 79S334A eval board. It can be used to : - write one character on one display cell - write a "word" of four characters - write a string of more than four characters and scroll it with a delay. - clear the display - change the delay between scrolling Idtdisplay is a misc driver. Therefore it uses only a minor number (default 254). The major number (set to 10) is shared with others misc devices. $ mknod /dev/idtdisplay c 10 254 2) How to use the display ? ___________________________ * write : you can write on the device such as a file (the character string will scroll). For example : $ echo "See me scrolling" > /dev/idtdisplay * read : clean the device. Example: $ cat < /dev/idtdisplay * ioctl perform different fuctions : - IDTDISPLAY_IOCTL_CLEAN : clean the display, no arg. - IDTDISPLAY_IOCTL_WRITE_CHAR : write one char on the display at the specified location (see idtdisp_wc_struct) struct idtdisp_wc_struct { char ch ; /* character to display */ int nb ; /* cell number where the display start (from 0 to 3) [0|1|2|3] */ }; - IDTDISPLAY_IOCTL_WRITE_4 : write four chars on the display arg : a string of four characters - IDTDISPLAY_IOCTL_DELAY : set up a new delay between scrolling arg : an unsigned long delay (in ms) Ioctl function return -1 if it failled, 0 otherwise. For futher details look at the man page for each system call. 2) Module Command Line Parameters --------------------------------- minor = misc device's minor number delay = scrolling in ms 3) An example using idtDisplay --------------------------------- #include #include #include #include #include #include #include "idtdisplay.h" int main(int argc, char *argv[]) { int desc = 0 ; char ref[20] = "/dev/idtdisplay" ; char msg[5] = "hye!" ; if ( (desc = open(ref, O_RDWR)) < 0){ perror("error open") ; exit(1) ; } if( ioctl(desc, IDTDISPLAY_IOCTL_WRITE_4, (int) msg) < 0 ){ perror("write four char failed : ") ; close(desc) ; exit(1) ; } close(desc) ; return 0 ; } 4) Run And Stop the driver -------------------------- make sure /dev/idtdisplay exist. Otherwise it need to be created. ex : mknod /dev/idtdisplay c 10 254 As root : insmod idtdisplay.o rmmod idtdisplay 5) Generate technical documentation with doxygen ------------------------------------------------ This is implementation documentation. A doxygen options file (Doxyfile.cfg) is provided with the driver. You must update it and then run the following command : doxygen Doxyfile.cfg You can generate html, man, rtf or latex documentation.