The MAX3100 and OLED-based GPS positioning system design (1)

0 introduction

In microcomputer application system, serial data communication usually chip "> 8251 8251, but because of the communication baud rate is not high, cannot be applied to the crystal oscillator for higher system, which makes high speed, high speed transceiver data system does not apply" > 8251 chip transceiver data, but there is a need to support the MAX3100 8251 high-speed communications, the highest communication baud rate up to 230KBPS, low power, low voltage, supported design system for small size, than using external clock 8253 "> 8253 provides external clock signal.

New MAXIM company launched the MAX3100 UART chip

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MAX3100 support high-speed communications, the highest communication baud rate up to 230KBPS, low power, low voltage, supported design system for small size, than using external clock design printed edition 8253 size half also small. And to make software more reliable design and implement.

Organic light emitting display OLED is more than the liquid crystal display technology, advanced next-generation flat panel display technology, is the industry-recognized as the most promising next-generation display technology.

Organic light emitting display OLED (Organic Light Emitting Display) and liquid crystal display technology, with super thin, high brightness, wide viewing angle, self-luminous, response speed, adapt wide temperature range, seismic intensity, low power consumption, allows for flexible displays and other advantages, so the OLED screen is rapidly expanding its portable electronic products market share, on the application to apply to communications, mapping, railway, as well as weapons and other wild harsh environment.

1 main works

AT89C52 MCU system is mainly composed, the MAX3100 universal asynchronous receiver/transmitter, OLED display GPS-OEM plate, etc.

AT89C52 MCU through the MAX3100 receive GPS-OEM Board issued statement of NEMA, the software programming the calculated position information (including: latitude, longitude, altitude, speed, date, time, course, satellite status, etc.), the OLED screen is displayed. And through the MAX3100 will these positioning information to RS232 standard serial data output. System circuit schematic diagram shown in Figure 1.

2-chip and GPS-OEM data communication between Board

SCM and GPS-OEM data communication between the Board, through the MAX3100 universal asynchronous receiver/transmitter, which shock frequency selection 11.0592MHz microcontroller.

First use the MAX232 level translation chip, came to realize the RS232 level and TTL level's bidirectional conversion, because the GPS OEM Board serial RS232 level is consistent with the standard level, while the MAX3100 is TTL level.

MAX3100 DIN pins for serial data input, DOUT as serial data output, serial clock of the rising edge latch DIN data, DOUT data from serial clock falling edge synchronization output.

MAX3100 DIN and DOUT pin serial data sequences are 16-bit data, including the former DIN data sequences of two characterization of string data types. The current two is "1,1", it indicates that the write command, the current two-digit is "0, 0", it indicates that the reading of data, the current two is "1, 0," said write data.

Initializes the MAX3100 is configured through the write command sequence microcontroller.

The command sequence including parity bit, data bits, stop bits, baud rate, word length, validate data FIFO, interrupt-enabled information. MAX3100 has its own baud rate generator, the oscillator frequency can be used as 1.843 2 MHz or 3.6864 MHz crystal oscillator. The baud rate by the write command sequence after a 4-bit B0-B3-bit.

When the SCM receives GPS OEM Board serial data by reading the MAX3100 data sequence to complete, single-chip from the MAX3100 readout of data needs in DIN writes a 16-bit words (0000H), and then reads from DOUT 16-bit words, where the high eight is: receive/send buffer State, data wrong/overflow State, receive/parity bit status and the status of the CTS, the low eight bits is the received GPS OEM Board serial data.

When the SCM sends your final positioning data is passed to the MAX3100 write data sequence to complete, single-chip data written to the MAX3100, written in the DIN is a 16-bit words, where high eight bit set is: Write flag, allow TX output, RTS pin set and deliver parity bit set.

It is the low eight bits of data to be transferred.

3 OLED display shows the positioning information

Display module display 128 columns, 64 rows, 1 tablet line drives and 2 pieces of columns, line drive drive 64 output, each column drive 64-channel output.

As long as you provide the power to produce the drive signal and synchronization signals, module external signal drive only with columns. Column drive built-in 64 × 64-bit display memory, each pixel on the display shows the status and display memory to display all data one-to-one, memory data directly as a graphical display of driving signal, when the "1", "O" when being displayed. OLED display in latitude, longitude, altitude, speed, date, time, course, satellite position positioning information.

4 software design

4.1 watchdog interrupt the application of

The 6 foot MAX706 and 7 feet respectively and P1.7 and reduction of AT89C52 feet attached to the software program, every other

Program inserts a watchdog counter reset instructions, which, in the program is running, if you enter an endless loop or illegal code areas, will make the system reset, ensure the system is up and running.

4.2 delay processing

Will have to send data into the send buffer, because the MAX3100 wait T = 1, send buffer is empty before you can receive another send data, so that there isn't a suitable delay, is necessary to ensure the accuracy of the data.

4.3 build font libraries

In the implementation of the first OLED display will need to display Chinese characters form a Chinese fonts, English characters or digits form a Latin character set.

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