内部上拉电阻用作带外部电容的滤波器

不，电阻器必须与信号串联以形成RC滤波器。这些电阻器与信号并联。



      以下为原文

    No, the resistor has to be in SERIES with the signal to form an RC filter.
Those resistors are in parallel with the signal.
 

      以下为原文

   

我不确定我理解你正在使用的键盘。如果它是一个16或20个小键盘，那么在使用最小引脚数的情况下，我使用了以下的成功。因为我们的PIC具有如此精确的ADC测量，您可以在PAD列引脚上创建一个电阻分压器梯形（即：可能是一系列1K（或10K或…？））。电阻之间的列，然后只是测量电压下降与一个模拟引脚与逻辑，以确定一个“按键”的电压读数来自该引脚。您还可以创建一个电阻分压器，通过一个交替电阻，如2K或.5K穿过垫排引脚。然后，只需测量电阻（通过电压降）如下：键列COL电阻无穷大=无键预设1 1 1 1.2k2 1 2.2 2.2K。3、1、3、3.2kA、1、4、4.2k4、2、1、1.4k5、2、2、2.4k6 2 3、3.4kb 2 2 4.4k7和1.6K等，ETCI使用这个键键垫（4x5），它在减少资源和房地产的同时工作，特别是如果使用电阻阵列时。选择你自己的电阻值，计算你自己的电压降。电阻器精度越高，测量就越容易。通过使用CASE类型命令简化解码。



      以下为原文

    I'm not sure I understand the keyboard you are using.  If it is a small 16 or 20 key pad then I've used the following with great success while using a minimum number of pins.
Because our PICs have such precise ADC measurements, you can create a voltage divider ladder of resistors across the pad column pins (ie: maybe a series of 1K (or 10K or...?)resistors between the columns and then just measure the voltage drop with one analog pin with logic to determine a "key pressed" by the voltage reading coming from that pin.  You can also create a voltage divider ladder of resistors across the pad row pins with an alternate resistance like .2K or .5K.  Then, just measure the resistance(via voltage drop) as follows:
 
KEY        Row  Col   resistance
                               infinity = no key pressed
1              1     1       1.2K
2              1     2       2.2K
3              1     3       3.2K
A              1     4       4.2K
4              2     1       1.4K
5              2     2       2.4K
6              2     3       3.4K
B              2     4       4.4K
7              3     1       1.6K  etc., etc
 
I've used this for 20 key pads (4x5) and it works while minimizing resources and real estate especially if you use resistor arrays.  Choose your own resistor values and calculate your own voltage drops.  The greater the resistors precision, the easier it is to measure.  Simplify decoding by using a CASE type command.

HII认为主要的问题在于内部拉起与碳电阻器有某种不同。它们是半导体电路，所以它们作为RC网络的一部分的行为可能不是预期的。但是，FWW，等效值通常大约100KHHIHEST。



      以下为原文

    Hi
 
I think the main question lies in that the internal pull-ups are somehow different from a carbon resistor.
They are semiconductor circuits so their behaviour as part of an RC network may not be as expected.
 
But, FWIW, the equivalent value is usually around 100K.
 
HIH
 
 
Best regards
Jorge
 
 

谢谢你的回答。我用下面的按钮做了一个键盘：我已经在PIC18系统中设计过它，我在这个新项目中可能遇到的问题是，也有一些RF模块会在键盘上产生噪音，而我的空间很小。出于这个原因，我想利用内部电阻结合外部电容器来消除这些模块产生的可能的噪声。



      以下为原文

   

Thanks for answering. I am making a keyboard with the following buttons:






I have already designed it before in a system with PIC18, the possible problem that I will have with this new project is that there are also some RF modules that may generate noise on the tracks that make up the keyboard and I have very little space. For that reason I want to take advantage of internal resistances in conjunction with external capacitors to eliminate possible noise generated by these modules.

如图所示的电容器应尽量减少进入PIC的任何射频噪声。只要它们被放置在非常接近输入引脚，并且在预期的频率上具有低ESR。如果这些是Schmitt Trigger输入也会有帮助。电容器将通过内部上拉充电到Vdd，相当于50-100K。因此，10纳秒电容器将充电到大约1毫秒的高逻辑电平。当按键被按下时，电容器几乎立即放电。这是一个好主意，添加代码，以检查它仍然为几个样本压几个毫秒分开。这也有助于高频噪声引起虚假点击。



      以下为原文

    The capacitors as shown should minimize any RF noise coming into the PIC. as long as they are placed very close to the input pins, and have low ESR at the frequencies expected. It will also help if these are Schmitt Trigger inputs. The capacitor will charge to Vdd through the internal pullup, which is equivalent to 50-100k. So a 10 nF capacitor will charge up to a high logic level in about 1 mSec. The capacitor will be discharged almost instantly when the key is pressed. It is a good idea to add code to check that it remains pressed for several samples a few mSec apart. That should also help with high frequency noise causing false clicks.

是的，电容器帮助。OP应该清楚，虽然上拉电阻器没有形成RC滤波器，因为正如我所说，它们不是与要过滤的信号串联。



      以下为原文

    Yes, the capacitors help.
The  OP should be clear though that the pullup resistors are not forming RC filters, because as I said, they are not in series with the signal to be filtered.
 

你是对的，电阻器必须与电容器串联，我必须明确地放置外部电阻器。



      以下为原文

   
 
You are right, the resistors must be in series with the capacitors, I must definitely place external resistors.
 

是的，但我们已经解决了。-）作为输出而不是输入引脚的上拉/下拉引脚。艾伯特



      以下为原文

   


Right, but  we have workaround about it. ;-)
Pullup/pulldown pins working as output and not for input pins.
 
Albert

是的，但我们已经解决了。-）上拉/下拉引脚作为输出而不是输入引脚。艾伯特？这和我们讨论的有什么关系吗？



      以下为原文

   


Right, but  we have workaround about it. ;-)
Pullup/pulldown pins working as output and not for input pins.
 
Albert
?? Does that have any relevance to what we are discussing?

是的，如果你真的看不到。如果我们把上拉/下拉作为输出信号，那么它的重发是与信号串联的，因此外部C在线程标题中创建RCROW PASS过滤器。对于来自第1位的Autor问题的回答是：1。是的，可以创建该过滤器。2。我们可以在矩阵键盘中使用这个过滤器。如上所述的软件技巧。艾伯特



      以下为原文

    Yes, if you realy don't see it.
 
If we togle pullup/puldown as output signal then its resitance is in serial with signal, thus with external C creates RC
low pass filter as in  thread title.
Answer for autors questions from post #1 are:
1. YES it is possible to create that filter.
2. We can use this filter in matrix keyboard. As above with software tricks.
 
Albert
 

？将输入引脚切换到输出以产生RC滤波器是没有意义的。代替串联电阻，可以通过在输入线路上在PCB上附着铁氧体条来降低噪声，但这将是笨重的，并且可能不太好。如果在矩阵键盘上的带状电缆上安装铁氧体翻盖可能是有效的，如果按键按下中断，高频噪声可能是一个问题，但是轮询与软件滤波应该足够了。如果RF能量足够高，进入PIC并造成破坏，那么它也可能是其他输入的问题。解决的办法是减少电磁干扰的来源。或者结合仔细的PCB布局（如接地平面）和屏蔽。



      以下为原文

    ?? It makes no sense to toggle an input pin to an output to create an RC filter.
 
In lieu of adding series resistors, it might be possible to reduce noise by attaching a ferrite strip on the PCB over the input lines, but that would be bulky and probably wouldn't do much good. It may be effective if a ferrite clamshell is installed on the ribbon cable for the matrix keypad.
 
High frequency noise might be a problem if key presses trigger an interrupt, but polling along with software filtering should be sufficient. If RF energy is high enough to get into the PIC and create havoc, it will probably be a problem for other inputs as well. The solution would be to reduce the source of the EMI. or to incorporate careful PCB layout (such as ground planes), and shielding.

你说得对。但我从来没有说过我的观点是创建最好的矩阵键盘应用程序。有时我们有最终的产品，并且想要改变他们的功能性，而构造者认为这是不可能的。艾伯特



      以下为原文

    You have right.
But I never said that my point is to create best matrix keyboard application.
Sometimes we have final product and want to change their funcionality in a way that constructor don't  thought it is possible.
 
Albert