1. The overall scheme design of the system
The system uses a new generation of 32bitRISC processor STM32 as the main control chip, transmits data via Ethernet, uses FLASH as a storage module, and FPGA completes the high-speed scanning and refreshing of the LED display. When the system is working, the upper computer is used to edit the display information, and the display information is transmitted to the microprocessor through the Ethernet interface, and the microprocessor writes the data information into the FLASH memory after receiving the data information. When displaying, the microprocessor reads the data in the FLASH, sends the data to the FPGA in parallel via the bus, and the FPGA transmits the data to the LED display screen for display after processing.
2. System hardware design
This system uses ST's new 32-bit microprocessor STM32F103ZET6 as the main control chip. STM32F103ZET6 uses the advanced architecture of the ARMCortex-M3 core. Its flexible static memory controller makes it easy to connect to many memories and peripherals. At the same time, STM32 has abundant peripherals on-chip, which can simplify the design of system peripheral circuits.
2.1 FLASH memory circuit design
FLASH uses Samsung’s K9F1G16U0M, which is a NAND-type FLASH with a storage capacity of 64M16 bits and a working voltage of 3.3V. The connection between STM32F103ZET6 and K9F1G16U0M in the system is shown in Figure 2. IO0~IO7 of FLASH memory are connected to the lower 8 bits of FMSC data bus, STM32 processor accesses the memory through FSMC; the chip select signal nCE of FLASH memory is connected with FSMC_NCE2 of FSMC, so that the address space of the memory is 0x70000000~077FFFFFFFF; FLASH memory The R/nB is connected to the FSMC_NWAIT pin of the STM32 processor. The processor uses R/nB as an interrupt source, so other tasks can be performed during the waiting period of the memory.
2.2 Ethernet interface circuit design
The Ethernet interface is used instead of the traditional serial port, which speeds up data transmission and can realize remote control at the same time. The STM32F103ZET6 chip does not integrate Ethernet MAC and PHY functions, but its FSMC supports the expansion of the Ethernet control chip. This system expands a piece of DAVICOM’s DM9000A chip on the FSMC to expand the STM32F103ZET6.
STM32F103ZET6 accesses DM9000A through FSMC. For STM32F103ZET6, DM9000A is a static memory peripheral. DM9000A adopts 16-bit mode, the data lines SD0~SD15 are directly connected to the low 16 bits of the FMSC data line FSMC_D0~FSMC_D15; the DM9000A chip selection signal line nCS is connected to the FSMC chip selection signal FSMC_NE4, so the DM9000A port address is 0x6c000000; the interrupt signal line of DM9000A INT can be directly connected to the IO port of STM32F103ZET6, and the interrupt multiplexing function of the processor IO port is activated in the program. STM32 receives network card data in interrupt mode.
