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2013年全国大学生电子设计竞赛

手写绘图板（G题）

【本科组】

2013年9月7日

2013全国大学生电子设计竞赛

手写绘图板

摘要

手绘板，众所周知，是计算机输入设备的一种，通常是由一块板子和一支压感笔组成。它和本文所介绍的手写绘图板等作为非常规的输入产品相类似，都针对一定的使用群体。手写绘图板主要是利用一根连接到电路的普通表笔在PCB覆铜板上实现简单的绘图及坐标查找功能，并能在表笔接触板上任一点时，明确显示触点的象限位置及坐标值。它包括硬件电路和软件编程两部分。硬件电路主要包括恒流源、二级差分放大、单片机内部A/D采样模块、显示模块。由于敷铜板的电阻很小，所以是采集小信号，然后将采集到的两路电压信号差分放大后经过二级放大得到一个稳定变化的电压值，然后用AD采样经数值变换得到坐标，用低功耗单片机MSP430F14处理，在HB240128液晶显示屏上显示。 采集若干点在液晶上描点还可以绘制一些简单的图形。

【关键字】 MSP430F149 敷铜板 差分放大 AD采样 低功耗

Handwritten Drawing Board

Abstract：Hand-painted plates, we all know, is a computer input device, which is

usually caused by a board and a pressure sensitive pen components. It is described in this article handwriting and drawing board unconventional inputs such as similar products are used for certain groups. Handwriting mainly using a graphics tablet connected to the circuit common table pen on the PCB CCL simple graphics and coordinate search function, and can contact board office table pen point, clearly shows the location and contact quadrant coordinate values. It includes hardware circuitry and software programming in two parts. Hardware circuit includes a constant current source, two differential amplifier, internal microcontroller A / D sampling module, display module. Since Bonded Copper resistance is small, so small signal is collected and then collected two amplified differential voltage signal amplified through two changes to get a stable voltage value, and then use AD sampling by numerical transform coordinates, with a low processing power microcontroller MSP430F14 in HB240128 displayed on the LCD. Collected at several points on the LCD can also draw on the tracing point some simple graphics.

【Keywords】 MSP430F149 A/D sampling Copper Differential amplifier

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手写绘图板（G题）

2013全国大学生电子设计竞赛

目录

一、引言........................................................................................................................ 1

1.1 系统总体框架............................................................................................... 1 1.2 本设计应该达到的技术指标....................................................................... 1

1.2.1 基本要求.......................................................................................... 1 1.2.2 发挥部分............................................................................................ 1

二、系统方案选择与论证............................................................................................ 2

2.1 系统方案选择............................................................................................... 2 2.2 主控器件的选择............................................................................................. 2 2.3 稳压电路的选择.......................................................................................... 3 2.4 运放的选择.................................................................................................. 4 三、系统总体设计........................................................................................................ 5

3.1 系统总体硬件电路框图.............................................................................. 5 3.2 系统软件框图............................................................................................ 5 四、系统单元电路设计................................................................................................ 6

4.1 恒流源电路.................................................................................................. 6 4.2 信号采集电路.............................................................................................. 7 4.3 二级差分放大电路...................................................................................... 7 4.4 负电压产生电路.......................................................................................... 7 五、系统测试与数据分析............................................................................................ 8

5.1 测试仪器...................................................................................................... 8 5.2 相关测试数据................................................................................................. 8 5.3 测试结果分析.............................................................................................. 9 六、重要程序解析........................................................................................................ 9

6.1 A/D采样程序............................................................................................... 9 6.2 拟合算法程序............................................................................................. 10 七、结论与系统改进措施 ......................................................................................... 12

7.1 题目达到了所有基本和部分扩展功能及指标的要求： ......................... 12

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手写绘图板（G题）