Designing a low-power Chinese human-machine interface based on TMS320LF2407

　　introduction

　　In modern intelligent instruments and equipment, graphic dot matrix liquid crystals that can display Chinese characters and small keyboards that can input information have become indispensable components of the human-machine interface of intelligent equipment. At the same time, the low power consumption feature also runs through the design of the Chinese human-machine interface. In recent years, with the emergence of low-price, high-performance DSP chips, DSP has been increasingly used in fields such as digital motor control, high-speed signal acquisition, voice processing, image analysis and processing, and increasingly shows its huge advantages. sex. The LCD screen is used as the display front-end of various portable systems because of its intuitive display and easy operation. Traditional LCD displays are often controlled by microcontrollers. However, when the system has a large amount of high-speed real-time data, the single-chip microcomputer becomes unable to do so due to the limitation of processing speed. In order to solve these problems, this article proposes a design of an LCD screen controlled by the high-speed and low-power DSP chip TMS320LF2407, which effectively solves the above problems.

　　In the design, the author uses TMS320LF2407 as the system control chip, and builds a low-power Chinese human-machine interface at the 3V level by selecting an appropriate liquid crystal display module. This Chinese human-machine display interface is an important part of the motion control system with TMS320LF2407 as the core.

　　1. TMS320LF2407 DSP

　　TMS320LF2407 is a 16-bit fixed-point DSP launched by Texas Instruments (TI). It has the basic functions of TMS320 series DSP and also has the following features:

　　1. Using high-performance static CMOS technology, the power supply voltage is reduced to 3.3V, reducing the power consumption of the controller.

　　2. It contains up to 32K×16-bit Flash program memory, up to 2.5K×16-bit data/program RAM, 544×16-bit dual-port RAM (DARAM), and 2K×16-bit single-port RAM (SARAM).

　　3. Two event management modules EVA and EAB. The event management module is suitable for controlling AC induction motors, brushless DC motors, switched reluctance motors, stepper motors, multi-stage motors and inverters.

　　4. The scalable external memory has a total of 192K×16 bits, of which the program memory space, data memory space, and I/O addressing space are each 64K×16 bits.

　　5. Contains watchdog timer (WDT), 10-bit ADC converter, controller area network module CAN2.0 B, serial communication interface module (SCI), 16-bit serial external device interface module (SPI), Phase locked loop based clock generator.

　　6. 5 external interrupts (two motor drive protection, reset and two maskable interrupts); 3 low-power power management modes, which can independently transfer peripheral devices into low-power working modes.

　　In addition, the chip has up to 41 general-purpose I/O pins (GPIO) that can be individually programmed or multiplexed. Users can set the software according to their own needs, giving it great flexibility in applications. In summary, TMS320LF2407 has extremely low power consumption, powerful processing capabilities, rich on-chip peripheral modules, and convenient and efficient development methods.

　　2. LCD module and interface circuit

　　In order to achieve a friendly Chinese human-computer display interface, the LCD module uses Truly's MG-12232. The typical supply voltage of this module is 3V, the typical operating current is 0.3μA, and its display range is 122×32 dot matrix. Its controller is two pieces of SED1520F0A. SED1520F0A can work normally at 3.3V voltage, thus avoiding the problem of logic level mismatch with TMS320LF2407.

　　A SED1520F0A can control an 80×16 dot matrix display. Its display RAM has a total of 16 lines, divided into 2 pages, with 8 lines per page. The data registers of each page correspond to 8 lines of points on the LCD screen. When setting the page address and column After the address, a certain unit of the display RAM is determined. Each column on the screen corresponds to a byte content of the display RAM, and the bottom bit of each column is the highest bit, and the top bit is the LSB, that is, the byte data of the RAM unit is from low to high, and each data bit corresponds to the display The 8 data bits from high to low in a column on the screen. Assigning a value to a byte unit of the display RAM is to control whether the pixels of the 8 rows (page) of the current column are displayed. When the data bit is "1", it is displayed, and when it is "0", it is not displayed.

　　The interface signals between SED1520F0A and TMS320LF2407 are (using M6800 timing):

　　DB0～DB7: Data bus; A0: Data/command selection signal, A0=1 means data appears on the data bus, A0=0 means instructions or read status appears on the data bus; : Interface timing type selection, =1 is M6800 timing, its operating signals are E, R/W, =0 is Intel8080 timing. In M6800 timing, R/W=1 is for reading and R/W=0 is for writing. When E1=1, the E1 block is selected, that is, the left half of the LCD module works. When E2=1, the E2 block is selected, that is, the LCD module works on the right half of the screen.

　　The interface circuit between TMS320LF2407 and MG-12232 module is shown in Figure 1. The corresponding control pins of TMS320LF2407 are set to I/O port mode, and software is used to simulate the M6800 operation sequence. In Figure 1, V0 is the negative voltage driving power input terminal required by the LCD. Its external resistor should be debugged with an adjustable resistor first to avoid inappropriate driving voltage and invisible display.

　　3. Keyboard interface

　　 Based on the consideration of low power consumption requirements of the system, the keyboard input response program should be designed to run in interrupt mode. That is, when a key is pressed, the DSP external interrupt 1 (XINT1) generates an interrupt (can wake up from the sleep state), and starts a 20ms timer to eliminate jitter and eliminate interference, and then the DSP enters the sleep state. When the 20ms timer generates an interrupt, the DSP is woken up from the sleep state again. At this time, the keyboard is scanned to determine whether a key is pressed. If a key is pressed, the key value is read from IOPB0 to IOPB7 and the corresponding key value is executed. function program. After executing this program, the DSP can enter sleep again and be in a low power consumption state.

　　4. Software design

　　The main program flow chart is shown in Figure 2.

　　Before the LCD module displays information, the LCD module must be initialized. The initialization flow chart is shown in Figure 3.

　　The DSP system initialization program and key scanning program are given below.

　　DSP system initialization program:

SYS: SETC INTM; disable maskable interrupts

CLRC CNF; B0 is configured as data storage space

SPLK? #81FEH, SCSR1; clock multiplied by 4

;CLKIN=6MHZ, CLKOUT=24MHZ

SPLK #0E8H, ; disable watchdog

LDP? #0

SPLK? #0001H, IMR; enable interrupt level 1 INT1

SPLK #0FFFFH, IFR; clear all interrupt flags

CLRC INTM; enable interrupt

RET

　　LCD initialization procedure:

LDP #0E1H; DP (7080H～70FFH)

LACL MCRA

AND #000FH? ;Configure IOPA[4～7], IOPB[0～7] is

;General I/O port function

SACL PADATDIR

OR #0F000H; IOPA[4～7] is the output mode

AND #0FF0FH; IOPA[4～7]=0

SACL PADATDIR

LDP #5H

SPLK #00E2H, LCDCMD; reset command E2H

CALL COMWE

SPLK #0A4H, LCDCMD; normal display driver command A4H

CALL COMWE

SPLK #0A9H, LCDCMD; duty cycle is 1/32

CALL COMWE