[Shanghai Hangxin ACM32F070 development board evaluation] 4. LCD_TK program analysis

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[Shanghai Hangxin ACM32F070 development board evaluation] 4. LCD_TK program analysis [Copy link]

 

I ran the LCD_TK example and was shocked by its speed.

I am also a fan of dot matrix display screens. I find some menus very complicated and not very fast when searching. However, this program makes a beep when I touch it with my hand, which seems very flexible.

So I was a little interested, could something I made be so useful and lovable? So I decided to analyze it.

The program itself is not too complicated. However, it is not too complicated. I spent a lot of time looking at it and finally understood it. It is roughly as follows:

1. Cycle detection of buttons, beeping as long as a button is pressed

2. Only when the OK button is pressed will the program be set to a set state, and when the program is run in the set state, the variable is:

fu8_Work_Mode

3. Use SYSTICK interrupt to count. When a certain amount is counted, set a variable to remember the previous state. This variable is:

gu8_time_count_free

The general process is like this. What surprised me is that these buttons are capacitors, so they need to be charged and discharged.

I looked at the schematic diagram as follows:

自电容检测原理框图见结构框图章节所示。比较器负端连接到采样电容 Cs，正端连接
TKEY模块的参考电压VREF输出。每个TKSCLK周期，通过对SW1和SW2的控制，OPA/LDO
输出的充电电压 VKEY 会先给外置通道按键分布电容 Cx 充电，然后 Cx 给 Cs 充电，一般情
况下 Cx（pF 级）的值远小于 Cs（nF 级）。经过多次充放电后 Cs 两端电压超过参考电压 VREF
时，比较器输出翻转；由一个计数器对 Cx 向 Cs 充电的次数（从单个通道扫描开始到比较器
输出翻转）进行计数，得到单次扫描的计数值。当手指和触摸按键靠近时，会引起 Cx 值发生
变化，扫描的计数值就会发生变化。通过计数值的变化可以测量出 Cx 上电容的变化，从而达
到触摸检测的目的。另外，电路上除了外置的 Cx 通道，还有一个内置扫描通道连接到补偿电
容 Cr，Cr 可以用于测量 Cs，在 Cx 电容小于 10pF 时，也可以通过使能 Cr 进行补偿；还有用
于防水控制和增加检测灵敏度的 Cshield 屏蔽通道。
一个通道扫描控制流程如下：
 使能检测通道，闭合 SWCX[n]（正常模式）或 SWCR（内置通道）；
 SW1,SW2 断开，SWCS 闭合，使得 Cs 对地放电；
 SW1,SW2,SWCS 断开，计数器清零；
 SW1 闭合，SW2 断开，OPA/LDO 给 Cx 充电；
 SW1 断开，SW2 闭合，Cx 给 Cs 充电，计数器加 1；
 重复上两个步骤直到 Cs 电压超过 VREF；
 比较器输出翻转，计数器结果锁存，并通过总线交给软件处理。

The development board has six buttons, each for one channel. I pressed each one very quickly but the development board responded accurately, which I found a bit incredible.

That is to say, every time I press it, the capacitor unit inside has been charged and discharged countless times.

lugl4313820

The development board has six buttons, each for one channel. I pressed each one very quickly but the development board responded accurately, which I found a bit incredible.

That is to say, every time I press it, the capacitor unit inside has been charged and discharged countless times.

This board is really good!