It is discussed that transplanting TCP / IP protocol stack LwIP on STM32 series MCU, and using the new Ethernet controller ENC24J600 to realize network data transmission function. The main function of this system is to receive the data sent by the host computer, and convert these data into a universal serial interface output. ENC424J600 is a new Ethernet controller from Microchip. Its speed is better than ENC28J60, and it provides users with two interface modes. This article introduces its implementation process based on SPI interface mode, and describes in detail the hardware circuit and software flow of the network card driver.
1 Introduction to ENC424J600
ENC424J600 is a separately available Fast Ethernet controller from Microchip. The connection method with MCU can adopt industry standard serial bus SPI or flexible parallel interface. The data rate of SPI interface can reach 14 Mb / s, and the speed of parallel interface can reach 140 Mb / s. ENC424J600 meets 10 basc-TX full-duplex, half-duplex mode, 100base-TX full-duplex, half-duplex mode, all four modes are in compliance with IEEE802.3 protocol. The chip has a built-in PHY physical layer and MAC media access control layer. The engine has RSA, DiffieHelman, AES, MD5, and SHA-1 algorithms. The chip is available in 44-pin TQFP and QFN packages. Another outstanding feature of this chip is that it has a 24 KB SRAM Buffer, which basically requires no external SRAM. The allocation of chip SRAM Buffer is shown in Figure 1.
SRAM Buffer is divided into two areas. Generally, the General Purpose Buffer is set as the sending area, and the RX FIFO Burfer is set as the receiving area. The two areas are distinguished by the pointer ERXST. The receiving area is usually set larger to prevent overflow of the received frame.
2 System hardware circuit design
2.1 Peripheral hardware circuit of network controller
There are several points to note in the peripheral hardware circuit design of the ENC424J600 network controller: The SPISEL pin of the ENC424J600 needs to be pulled up to the power supply through a 100kΩ resistor, so that the system can enter the SPI mode when powered on, and at the same time lead out the INT pin as a receive interrupt A capacitor should be connected between each power pin and ground. To better prevent interference, two capacitors were added during the design. When wiring, make the 0.01μF capacitor closer to the power pin; the RBIAS pin needs to be connected with a 12.4 kΩ To the ground; in addition, the connection of the RD + and RD-differential signals is different from the general network controller. It is not directly connected to the power supply through the resistor, so special attention is required. The Ethernet interface uses HR961160C. The socket integrates an Ethernet isolation transformer and LED lights. It is also a patch type and saves PCB board space. It should be noted that when routing PCBs, the traces of the two pairs of RD +, RD- and TD +, TD- should be symmetrical and as short as possible.
ENC424J600 peripheral hardware circuit and HANRUN Ethernet transformer socket peripheral circuit diagram are shown in Figure 2 and Figure 3.
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