Visible to Intel only — GUID: iga1401317116475
Ixiasoft
Visible to Intel only — GUID: iga1401317116475
Ixiasoft
12.4.1. HAL System Library Support
The Intel-provided driver implements a HAL character-mode device driver that integrates into the HAL system library for Nios® II and Nios® V processors systems. HAL users should access the JTAG UART via the familiar HAL API and the ANSI C standard library, rather than accessing the JTAG UART registers. ioctl() requests are defined that allow HAL users to control the hardware-dependent aspects of the JTAG UART.
For Nios® II and Nios® V processors users, the HAL system library API provides complete access to the JTAG UART core's features. Nios® II and Nios® V processors programs treat the JTAG UART core as a character mode device, and send and receive data using the ANSI C standard library functions, such as getchar() and printf().
The "Printing Characters to a JTAG UART core as stdout" example below demonstrates the simplest possible usage, printing a message to stdout using printf(). In this example, the Platform Designer system contains a JTAG UART core, and the HAL system library is configured to use this JTAG UART device for stdout.
#include <stdio.h> int main () { printf("Hello world.\n"); return 0; } |
The Transmitting characters to a JTAG UART Core example demonstrates reading characters from and sending messages to a JTAG UART core using the C standard library. In this example, the Platform Designer system contains a JTAG UART core named jtag_uart that is not necessarily configured as the stdout device. In this case, the program treats the device like any other node in the HAL file system.
/* A simple program that recognizes the characters 't' and 'v' */ #include <stdio.h> #include <string.h> int main () { char* msg = "Detected the character 't'.\n"; FILE* fp; char prompt = 0; fp = fopen ("/dev/jtag_uart", "r+"); //Open file for reading and writing if (fp) { while (prompt != 'v') { // Loop until we receive a 'v'. prompt = getc(fp); // Get a character from the JTAG UART. if (prompt == 't') { // Print a message if character is 't'. fwrite (msg, strlen (msg), 1, fp); } if (ferror(fp)) // Check if an error occurred with the file clearerr(fp); // If so, clear it. } fprintf(fp, "Closing the JTAG UART file handle.\n"); fclose (fp); } return 0; } |
In this example, the ferror(fp) is used to check if an error occurred on the JTAG UART connection, such as a disconnected JTAG connection. In this case, the driver detects that the JTAG connection is disconnected, reports an error (EIO), and discards data for subsequent transactions. If this error ever occurs, the C library latches the value until you explicitly clear it with the clearerr() function.
For complete details of the HAL system library, refer to the Nios II Software Developer's Handbook .
The Nios® II Embedded Design Suite (EDS) provides a number of software example designs that use the JTAG UART core.