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Issue #214 May 2008
Where Analog And Digital Collide
An Easy-To-Use LCR Meter
Third Place Microchip 2007 Design Contest
by Miguel Rusch
Start | LCR Meter | Back to Basics | The Big Picture | Creating a Wave | Analog Stages | Signal Conditioning | User Interface | Firmware | Take a Measurement | System Performance | Further Development | What's Next? | Sources & PDF
USER INTERFACE
You interact with the device via three control buttons. You receive information via a 128 × 64 pixel graphic LCD using a Toshiba T6963C chipset. The eight data lines are driven via an MCP23S08 SPI GPIO. The RD signal is supplied as an inversion of the WR signal via a general-purpose NPN transistor rather than using an additional GPIO line. The two remaining control lines, CE and C/D, are driven directly from general I/O pins.
The screen contrast is controlled by a connection to a PWM pin clocked at 1 MHz (required for DDS operation). Currently, the contrast is not user-adjustable, although this functionality will be added in a later revision. Similarly, backlighting control is not implemented in the prototype. This is required to improve battery life.
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