tailieunhanh - Practical Arduino Cool Projects for Open Source Hardware- P36

Practical Arduino Cool Projects for Open Source Hardware- P36: A schematic or circuit diagram is a diagram that describes the interconnections in an electrical or electronic device. In the projects presented in Practical Arduino, we’ve taken the approach of providing both a photograph and/or line drawing of the completed device along with a schematic. While learning to read schematics takes a modest investment of your time, it will prove useful time and time again as you develop your projects. With that in mind, we present a quick how-to in this section | CHAPTER 15 VEHICLE TELEMETRY PLATFORM provide the specific features required by the project all to reduce memory usage. This is a classic situation where a prewritten library might make things simpler from a development point of view but in the end it just takes up too much space and needs to be replaced by minimal custom-written functions. Just as in the Water Flow Gauge project we re going to drive the LCD in 4-bit mode to save on wiring and I O pins but the MPGuino OBDuino codebase on which we based this project also includes a couple of extra features that are quite handy backlight control and contrast control. If you are going to leave your car engine datalogger permanently connected it s important to minimize the power it drains from your car battery while the engine isn t running and an LCD backlight can use a significant amount of power. MPGuino OBDuino includes a display-blanking feature that uses a transistor to turn on the display backlight only when it s needed and then blank it when the engine isn t running. It also uses PWM pulse-width modulation from an Arduino digital pin to vary the brightness giving you more than simple on off backlight control. The LCD needs to be wired up in almost the same way as the display in the Water Flow Gauge project using a strip of ribbon cable to connect ground 5V RS Enable and D4 through D7. Unlike the Water Flow Gauge project though we will also control the backlight from the Arduino rather than hardwire it to a fixed level using a resistor. The pin assignments are given in Table 15-6. Table 15-6. Connections from Arduino to HD44780 LCD module Arduino Pin LCD Pin Label Name Description GND 1 GND Ground Display ground connection 5V 2 VCC Power Display 5V connection Digital OUT 6 3 Vo Contrast Contrast adjustment voltage Analog IN 0 4 RS Register Select Data HIGH Control LOW GND 5 R W Read Write Read HIGH Write LOW Analog IN 1 6 E Enable Enable byte nibble transfer 7 D0 DataO Data bit 0 8 D1 Data1 Data bit 1 9 D2 Data2

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