Intercom dtmf decoding

1. Introduction
Mainly solves the problem that some walkie-talkies do not have dtmf decoding function
. It can also be used for radio remote control, such as the remote opening and closing functions of the repeater station.
2. MT8870 module
Figure 2-1 MT8870-dtmf-decoding module schematic
 
 
                                          Figure 2-2 MT8870-dtmf-decoding table
 
 
3. The serial port screen
uses Taojingchi 7-inch serial port screen
or other Taojingchi screens with extended IO
                                            Figure 3-1 Extended IO
 
                               Figure 3-2 Taojingchi function selection table
 
You can also use an esp8266 development board + Taojingchi's cheapest serial port screen (without extended IO)
This method uses the serial port screen only as a display device, and data analysis is done on esp8266.
You can also connect esp8266 to a computer without a serial port screen and use the computer to display it.
4. Code part
The code used here is very simple.
Mainly when the screen is full, you need to delete the top data to achieve automatic scrolling
spstr t0.txt,t2.txt,"
",0spstr t0.txt,t3.txt,"
",16strlen t2.txt,len.valif(t3.txt!="") { len.val+=2 substr t0.txt,t0.txt,len.val,500 }
                                            Figure 4-1 Serial screen page
5. Finished product
6. Attachments
dtmf.HMI - This is the software of Taojingchi serial screen, which can be used to edit and upload programs to the serial screen
dtmf.tft - This can be placed in the root directory of the memory card to directly download the program to the serial screen without software