unsigned int enc28j60_receive_packet(unsigned int maxlen, unsigned char *buffer)
{
unsigned int rxstat;
unsigned int len;
//packet in buffer ?
if ((enc28j60_read_address(ENC28J60_REG_EIR) & (1<<ENC28J60_BIT_PKTIF)) == 0){
//double check!
//errata says that PKTIF does not work as it should
//->check packetcount too:
if (enc28j60_read_address(ENC28J60_REG_EPKTCNT) == 0)
return 0;
}
//set read pointer to next packet;
enc28j60_write_address(ENC28J60_REG_ERDPTL, (enc28j60_next_packet_ptr));
enc28j60_write_address(ENC28J60_REG_ERDPTH, (enc28j60_next_packet_ptr)>>8);
//now read the transmit status vector
//read next packet ptr
enc28j60_next_packet_ptr = enc28j60_spi_read_byte(ENC28J60_OP_READ_BUF_MEM, 0);
enc28j60_next_packet_ptr |= enc28j60_spi_read_byte(ENC28J60_OP_READ_BUF_MEM, 0)<<8;
//read packet length
len = enc28j60_spi_read_byte(ENC28J60_OP_READ_BUF_MEM, 0);
len |= enc28j60_spi_read_byte(ENC28J60_OP_READ_BUF_MEM, 0)<<8;
//read rx stat
rxstat = enc28j60_spi_read_byte(ENC28J60_OP_READ_BUF_MEM, 0);
rxstat |= enc28j60_spi_read_byte(ENC28J60_OP_READ_BUF_MEM, 0)<<8;
//limit read bytecount
if (len>maxlen)
len = maxlen;
//transfer packet from enc28j60 to our buffer
enc28j60_read_buffer(buffer,len);
//mark packet as processed (free mem)
//ERRATA says we need to check packet pointer:
if ((enc28j60_next_packet_ptr- 1 < ENC28J60_RX_BUFFER_START) || (enc28j60_next_packet_ptr- 1 > ENC28J60_RX_BUFFER_END)){
enc28j60_write_address(ENC28J60_REG_ERXRDPTL, LO8(ENC28J60_RX_BUFFER_END));
enc28j60_write_address(ENC28J60_REG_ERXRDPTH, HI8(ENC28J60_RX_BUFFER_END));
}else{
enc28j60_write_address(ENC28J60_REG_ERXRDPTL, LO8(enc28j60_next_packet_ptr- 1));
enc28j60_write_address(ENC28J60_REG_ERXRDPTH, HI8(enc28j60_next_packet_ptr- 1));
}
//decrement packet counter:
enc28j60_spi_write_word(ENC28J60_OP_BFS|ENC28J60_REG_ECON2, (1<<ENC28J60_BIT_PKTDEC));
return len;
}
/**
* Fetches a pending packet from the RAM buffer of the ENC28J60.
*
* The packet is written into the given buffer and the size of the packet
* (ethernet header plus payload, exclusive the CRC) is returned.
*
* Zero is returned in the following cases:
* - There is no packet pending.
* - The packet is too large to completely fit into the buffer.
* - Some error occured.
*
* \param[out] buffer The pointer to the buffer which receives the packet.
* \param[in] buffer_len The length of the buffer.
* \returns The packet size in bytes on success, \c 0 in the cases noted above.
*/
uint16_t enc28j60_receive_packet(uint8_t* buffer, uint16_t buffer_len)
{
if(!enc28j60_read(EPKTCNT))
return 0;
/* set read pointer */
enc28j60_write(ERDPTL, packet_ptr & 0xff);
enc28j60_write(ERDPTH, packet_ptr >> 8);
/* read pointer to next packet */
packet_ptr = ((uint16_t) enc28j60_read_buffer_byte()) |
((uint16_t) enc28j60_read_buffer_byte()) << 8;
/* read packet length */
uint16_t packet_len = ((uint16_t) enc28j60_read_buffer_byte()) |
((uint16_t) enc28j60_read_buffer_byte()) << 8;
packet_len -= 4; /* ignore CRC */
/* read receive status */
enc28j60_read_buffer_byte();
enc28j60_read_buffer_byte();
/* read packet */
if(packet_len <= buffer_len)
enc28j60_read_buffer(buffer, packet_len);
/* free packet memory */
/* DS80349C.errata #14 */
uint16_t packet_ptr_errata = packet_ptr - 1;
if(packet_ptr_errata < RX_START || packet_ptr_errata > RX_END)
packet_ptr_errata = RX_END;
enc28j60_write(ERXRDPTL, packet_ptr_errata & 0xff);
enc28j60_write(ERXRDPTH, packet_ptr_errata >> 8);
/* decrement packet counter */
enc28j60_set_bits(ECON2, (1 << ECON2_PKTDEC));
if(packet_len <= buffer_len)
return packet_len;
else
return 0;
}
