Ethernet controller ENC28J60 configured with single-chip "e-mailman" system

1 Overview

With the development of the Internet, in order to facilitate people to receive emails in real time, this article introduces an "e-mailman" system based on a single-chip microcomputer and Labview. The PC program is written using Labview, and the network communication function is realized by connecting the single-chip microcomputer with the Ethernet controller ENC28J60, and the received emails are displayed through the LED. In order to simplify the system design, this system adopts the method of directly sending 16×16LED dot matrix data. This method can remove the design of the single-chip Chinese character dot matrix library, greatly simplifying the design and reducing costs.

2. Hardware structure

The hardware structure of the e-mailer is shown in the figure above. The single-chip microcomputer uses the AT89C51ED2 launched by ATMEL, which has 64K bytes of FLASH, 2K bytes of RAM, 2K bytes of EEPROM, supports online programming, 6 8-bit general-purpose I/O ports, hardware watchdog timer, serial peripheral interface (SPI) that can work in host and slave mode, 9 interrupt sources, 4 levels of interrupt priority, and 3 16-bit timer counters.

ENC28J60 is a new stand-alone Ethernet controller with only 28 pins launched by MICroChip, which is conducive to creating small, low-cost and streamlined embedded network systems. The ENC28J60 Ethernet controller uses the industry-standard SPI serial interface and only needs 4 lines to connect to the main control microcontroller. It has a built-in 10Mbps Ethernet physical layer device (PHY) and media access controller (MAC), which can reliably send and receive information packet data according to the industry-standard Ethernet protocol. ENC28J60 has programmable filtering functions, special filters, including Microchip's programmable pattern matching filters; it can automatically evaluate, receive or reject MagiCPACket, unicast (Unicast), multicast (Mul TI cast) or broadcast (Broadcast) information packets, reducing the processing load of the main control microcontroller: built-in programmable 8KB dual-port SRAM buffer, can realize flexible and reliable data management mechanism.

2.1 Connection between AT89C51ED2 and ENC2&J60

The ENC28J60 operates at 3.3V and is easily integrated into a 5V system. The SPI's CS, SCK, and SI inputs, as well as the RESET pin, can all withstand 5V: On the other hand, if the host controller runs at 5V, when the SPI and interrupt inputs are driven by the 3.3VCMOS outputs on the ENC28J60, it is likely that they will not meet the specification requirements, and a unidirectional level converter is required. This system uses an inexpensive 74HCT08 (quad AND gate) to provide the necessary level conversion. The conversion circuit is shown in the figure below, with the microcontroller working in host mode and the ENC28J60 working in slave mode.

2.2LED display module

The LED display circuit is shown in the figure above, which adopts row scanning. Among them, the P4 port controls the number of scan rows, the P2 port controls the column register selection, and the PO port sends the LED dot matrix data. The dot matrix data of each word occupies 32 bytes. The single-chip microcomputer first selects the first row, and then selects the first 74LS244; then writes the first byte of the dot matrix data of the first word through the PO port, and then selects the second 74LS244; then writes the 17th byte of the dot matrix data of the first word through the PO port, and then selects the third 74LS244; then writes the first byte of the second word through the PO port, and then writes in sequence until the 17th byte of the dot matrix data of the 16th word; then selects the second row and scans in sequence.