Not able to send ethernet frame from FPGA to windows PC

#include <altera_avalon_sgdma.h>

# include <altera_avalon_sgdma_descriptor.h>

# include <altera_avalon_sgdma_regs.h>

# include "sys/alt_stdio.h"

# include "sys/alt_irq.h"

# include <unistd.h>

// Function Prototypes

void rx_ethernet_isr (void *context);

//void tx_ethernet_isr (void *context);

//void tx_ethernet_isr (void *context);

// Global Variables

unsigned int i=0;

// Create a transmit frame char=1 byte

unsigned char tx_frame[1518] = { 0 };

// Create a receive frame

unsigned char rx_frame[1518] = { 0 };

// Create sgdma transmit and receive devices

alt_sgdma_dev * sgdma_tx_dev;

alt_sgdma_dev * sgdma_rx_dev;

// Allocate descriptors in the descriptor_memory (onchip memory)

alt_sgdma_descriptor tx_descriptor __attribute__ (( section ( ".descriptor_memory" )));

alt_sgdma_descriptor tx_descriptor_end __attribute__ (( section ( ".descriptor_memory" )));

alt_sgdma_descriptor rx_descriptor __attribute__ (( section ( ".descriptor_memory" )));

alt_sgdma_descriptor rx_descriptor_end __attribute__ (( section ( ".descriptor_memory" )));

/********************************************************************************

* This program demonstrates use of the Ethernet in the DE2-115 board.

*

* It performs the following:

* 1. Records input text and transmits the text via Ethernet after Enter is

* pressed

* 2. Displays text received via Ethernet frame on the JTAG UART

********************************************************************************/

int main(void)

{

// Open the sgdma transmit device

sgdma_tx_dev = alt_avalon_sgdma_open ("/dev/sgdma_tx");

if (sgdma_tx_dev == NULL) {

alt_printf ("Error: could not open scatter-gather dma transmit device\n");

return -1;

} else alt_printf ("Opened scatter-gather dma transmit device\n");

// Open the sgdma receive device

sgdma_rx_dev = alt_avalon_sgdma_open ("/dev/sgdma_rx");

if (sgdma_rx_dev == NULL) {

alt_printf ("Error: could not open scatter-gather dma receive device\n");

return -1;

} else alt_printf ("Opened scatter-gather dma receive device\n");

// Set interrupts for the sgdma receive device

alt_avalon_sgdma_register_callback( sgdma_rx_dev, (alt_avalon_sgdma_callback) rx_ethernet_isr, 0x00000014, NULL );

// Create sgdma receive descriptor

alt_avalon_sgdma_construct_stream_to_mem_desc( &rx_descriptor, &rx_descriptor_end, (alt_u32 *)rx_frame, 0, 0 );

// Set up non-blocking transfer of sgdma receive descriptor

alt_avalon_sgdma_do_async_transfer( sgdma_rx_dev, &rx_descriptor );

// Triple-speed Ethernet MegaCore base address

volatile int * tse = (int *) 0x00102000;

// Initialize the MAC address

//*(tse + 3) = 0x116E6001;

//*(tse + 4) = 0x00000F02;

// Specify the addresses of the PHY devices to be accessed through MDIO interface

*(tse + 0x0F) = 0x10;

*(tse + 0x10) = 0x11;

// Write to register 20 of the PHY chip for Ethernet port 0 to set up line loopback

*(tse + 0x94) = 0x4000;

// Write to register 16 of the PHY chip for Ethernet port 1 to enable automatic crossover for all modes("| = OR")

*(tse + 0xB0) = *(tse + 0xB0) | 0x0060;

// Write to register 20 of the PHY chip for Ethernet port 2 to set up delay for input/output clk

*(tse + 0xB4) = *(tse + 0xB4) | 0x0082;

// Software reset the second PHY chip and wait

*(tse + 0xA0) = *(tse + 0xA0) | 0x8000;

while ( *(tse + 0xA0) & 0x8000 )

;

// Enable read and write transfers, gigabit Ethernet operation, and CRC forwarding

*(tse + 2) = *(tse + 2) | 0x000000CB;

alt_avalon_sgdma_construct_mem_to_stream_desc( &tx_descriptor, &tx_descriptor_end, (alt_u32 *)tx_frame, 60, 0, 1, 1, 0 );

// Set up non-blocking transfer of sgdma transmit descriptor

alt_avalon_sgdma_do_async_transfer( sgdma_tx_dev, &tx_descriptor );

// Wait until transmit descriptor transfer is complete

while (alt_avalon_sgdma_check_descriptor_status(&tx_descriptor) != 0)

;

return 0;

}

/****************************************************************************************

* Subroutine to read incoming Ethernet frames

****************************************************************************************/

void rx_ethernet_isr (void *context)

{

// Wait until receive descriptor transfer is complete

while (alt_avalon_sgdma_check_descriptor_status(&rx_descriptor) != 0);

// Create new receive sgdma descriptor

alt_avalon_sgdma_construct_stream_to_mem_desc( &rx_descriptor, &rx_descriptor_end, (alt_u32 *)rx_frame, 0, 0 );

// Set up non-blocking transfer of sgdma receive descriptor

alt_avalon_sgdma_do_async_transfer( sgdma_rx_dev, &rx_descriptor );

for(i=0;i<=1518;i++)

tx_frame=rx_frame;

for (i=0;i<=25;i++)

alt_printf("%x",rx_frame[i]);

alt_printf("\n");

alt_printf("%x",rx_frame[25]);

alt_printf("\n");

}

This is the complete code

If you're trying to use the SGDMA in Ethernet IP to receive and then transmit data, you've done only 50% of it. You can't do a loopback of RxD to TxD simply by doing

tx_buffer = rx_buffer.

What you've done here is only copy the contents of the Rx buffer to the Tx buffer. You seem to have created the rx_descriptors and used the Rx send function correctly. But you didn't do the same for the Tx. You need to uncomment the Tx buffers, descriptors and functions. Get the Rx Data to the rx_buffer as you've done, and in the for loop copy the buffer contents to tx_buffer. Then use the Tx descriptors functions , program the Tx_Desc and call the Tx send data function. This will now send the received data via the Tx lines over the Ethernet and you should be able to see the data at the other terminal.

Do keep in mind to account for the Tx buffer size, filling it up too soon will cause data loss.