LCDproc is meant to be modular, it is relatively easy to add new input and output drivers to LCDproc. Actually, there are a few things that you can do to make your life easier, they are listed here. This chapter will explain you the major steps and few gotchas of adding your own driver to LCDproc. Enjoy! Driving an LCD display is not easy; you need to address ports, to send bytes in a certain order, to respect timing, and unfortunaly no two operating system let you do this in the same way. But don't dispair! There's hope! Someone in a galaxy far far away, has allready done the dirty job for you! This dirty job has been put in shared files. These shared files are full cross platform and are automagically configured by the configure script. You only need to include them and use their functions to benefit from them. These files are provided only for drivers, others are provided for all of LCDproc. These files are located in the shared directory, they have a dedicated chapter in this book. The file port.h, located in the server/drivers/ directory provide Input/Output and port permissions for the PC compatible parallel port, also known as the LPT port. Of course, these functions will only work if the computer where LCDproc runs has parallel port!r In these situations, the configure script will see this and disable drivers that need a parallel port. port.h file defines 6 static inline functions for port I/O: static inline int port_in unsigned short int port Returns the content of the byte. static inline void port_out unsigned short int port unsigned char val Returns nothing (void). static inline int port_access unsigned short int port Returns 0 if successful, -1 if failed. static inline int port_deny unsigned short int port Returns 0 if successful, -1 if failed. static inline int port_access_full unsigned short int port unsigned short int count Returns 0 if successful, -1 if failed. static inline int port_deny_full unsigned short int port unsigned short int count Returns 0 if successful, -1 if failed. #include "port.h" /* Get access to these 3 ports: 0x378 (CONTROL), 0x379 (STATUS) and 0x37A (DATA) */ if ( -1 == port_access_multiple(0x378,3) ) { /* Access denied, do something */ } /* Write a 'A' to the control port */ ort_out(0x378, 'A'); /* Read from the status port */ char status = port_in(0x379); /* Close the 3 ports */ port_deny_multiple(0x378,3); adv_bignum.h is the headerfile for lib_bignum.a (made from adv_bignum.c) which contains everything needed to show big-numbers, including the fonts for the different displays. (All files are located in the server/drivers/ directory.) There are only a few requirements to the calling driver: The display's cellwidth has to be 5 (6 works also in some cases) and the cellheight 7 or 8. The following functions have to be implemented by the driver: chr() set_char() (only if the display has custom-characters) The custom-characters (if available) have to be at char 0, 1, 2, ..... ,n The library determines the correct font, depending on the display size and the number of user-defined characters itself. So it is easy to integrate into the driver. void lib_adv_bignum Driver *drvthis int x int num int height int do_init int customchars The main thing the driver has to do is to call this function from its num() function. Where num is the number (legal: 0 - 9, and :) to be written, height the display's height in characters and customchars the number of available custom characters. x is the x position of the top-left corner of the big-number (the big-numbers don't have a y position). The placing of the characters is done by the client, so the driver only has to forward the position to the lib. The bignumlib has no influence on the placing of the characters. If do_init is not 0 lib_bignum will set the custom characters of the display for the big-numbers. The driver has to check if the custom-characters have to be set or if it is already done and tell it to the lib (using the do_init parameter). The common way is to use variable called p->ccmode or similar. In the different drivers there are some differences in the naming and handling of this variable. So the responsibility of checking and setting is left at the driver. The only function of lib_adv_bignum() is to determine the best display-dependent big-number function for the given display parameters, and to call it. The display-dependent functions are named adv_bignum_num_N_M(). Where N is the display-height in lines and M the number of used user-defineable characters. The bits of the user-characters are stored in static char bignum (take a look at the source and you will see what I mean). (On a display with a cellheight of 7 the lowest line stored is not shown.) While static char num_map defines the placing in the big number. (A big number is always 3 characters wide and 4 characters high. On a big number for 2 line displays the 2 lower lines are not in use.) If user-characters have to be set the driver's set_char() function will be called once for every user-character. Now adv_bignum_write_num() is called. This function places the 6 or 12 characters the big-number consists of in the framebuffer using the drivers chr() function. Calling the lib_adv_bignum() from a drivers_num function. (from serialVFD.c): MODULE_EXPORT void serialVFD_num( Driver * drvthis, int x, int num ) { PrivateData *p = drvthis->private_data; int do_init = 0; if (p->ccmode != CCMODE_BIGNUM){ // Are the custom-characters set up correctly? If not: do_init = 1; // Lib_adv_bignum has to set the custom-characters. p->ccmode = CCMODE_BIGNUM; // Switch custom-charactermode to bignum. } // Lib_adv_bignum does everything needed to show the big-numbers. lib_adv_bignum(drvthis, x, num, p->height, do_init, p->customchars); } All that's left to do is to include the header-file #include "adv_bignum.h" and to add libbignum.a to the libs and adv_bignum.h sources of your driver in the Makefile (or the file that generates the Makefile).