eZ80 Serial Driver

DDK Sample Design
ZiLOG Application Note
How to create and install a XINU driver for eZ80 family of processors
Author: Andrei Kovalev
FAE ZiLOG Germany

Driver initialization

There are two methods of driver initialization. One method is direct where the driver initialized on its own and the physical channel initialized using control function. The other method is where the UART is initialized by IPWorks originally and then the driver is installed and used on that channel. This method is provided to allow the user to use the IPWorks serial API while working with the COM driver.

Using direct method is very simple. First, the con_init() function must be called to install the driver. After that the control function is used to setup the UART parameters. See the following example. 

  con_init();
  xprintf("\nSerial COM driver installed\n");

  hReceiver =
    open( hCOM1, "COM1:", (char*)0 );
  xprintf("\nOpened COM1:");

  // setup the serial port
  control( hReceiver, SET_RATE, (char*)56700, 0);
  // set the line control value
  control( hReceiver, SET_LINE, (char*)lcr_value , 0);
  // set the flow control
  control( hReceiver, SET_FLOW, (char*)COM_FLOW_HARD, 0);

Notice that the xprintf(char*) should be used as soon the port is opened.

To provide maximum compatibility to IPWorks and to avoid excessive reconfiguration most of the low level hardware initialization is left to be done by the IPWorks. Use the standard serparams structure of IPWorks to define the serial communication parameters. 

struct serialparam serparams[2] = {
    {57600, 8, 2, PARNONE, SERSET_ONLCR | SERSET_IGNHUP},
    {57600, 8, 1, PARNONE, }
  };

The serparams structure is defined in the serial_conf.c file which is typically can be located in the conf subdirectory of IPWorks installation.

the com_init() function is used to install the driver in a XINU device table. This function creates the two new serial devices - hCOM1 and hCOM2 and add the corresponding device entries to the XINU device table using the following command sequence 

  extern struct devsw comdev;
  int comdevice;

    if( (comdevice=adddevice( &comdev, 0)) != SYSERR )
    {
        devtab[comdevice]. dvinit(&devtab[comdevice]);
        . . .

The comdev structure of the type struct devws already exists in the driver and is taken from the library. The addevice function of XINU API uses this descriptor to put the structure information into the system device table devtab. The variable devtab is described in the conf.h header file.

As soon as a COM device is initialized and opened the interrupt for the corresponding UART is enabled. The character transmission and reception can then begin.

Documenation Index
Home | Downloads | eZ80 Module

1