Direct LCD Drive

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Example of duplexed LCD drive with ST6215x

The following example describes the drive in duplexed mode of an LCD with an ST6215. The

software is made in such way that no interrupt is generated and an OFF state for the LCD is

possible. The only components necessary are those to drive the ST62 (oscillator, reset,...) and

four resistors to generate the backplane intermediate voltages.

The ST6215 has 20 I/O pins, thus it is able to drive up to 36 LCD segments and 2 backplanes.

One digit is defined with 8 segments connected to 2 backplanes. Each digit can display 11 val-

ues, from 0 to 9 and no display.

Each value to be displayed is associated to a certain LCD waveform. One LCD waveform pe-

riod is separated in 4 steps corresponding to the 3 I/O configurations (1-0-input). A look-up ta-

ble stores the bytes which relate the I/O configuration to the value to display.

Figure 5. ST6215 based example