GPS Module with Time Display

Overview

The project exemplifies the permanent display of accurate time received from a cheap GPS module as it contains a PIC18F1320 microcontroller.

Explanation

The time display is being used with the on-chip 8MHz oscillator while driving a 6-digit LED display. The charlieplexing technique is used to drive the MAX6951 LED display in order to be multiplexed with further saving of chip pins. The use of MAX7219 is another alternative in place of a MAX6951 for better display brightness since it has an option to adjust the brightness and a serial interface.

During the operation, the serial data from a GPS module is received by the microcontroller at the standard rate of 4800 Baud. The NMEA 0183 standard data sentences is being parsed into two types of sentence including RMC and GGA. Data and time information are included in the RMC sentences while time and number of satellites received are included in GGA.

Through series of resistors, the three high efficiency dual LED digit common cathode type display segments are driven by the controller. This helps limit the current to remain within the drive limit and effectively reduces the average current by the simultaneous multiplexing action.