TTL/RS-232 level conversion module.
The product model on this page: Dual-channel pin header type MCS-51B
Used to convert 5V/3.3V level TTL serial port signal to RS-232 level serial port signal, or convert RS-232 signal to TTL serial port signal, two-way dual-channel simultaneous communication, stable support rate 460800bps (up to 921600bps ).
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1. The products of some stores distinguish between TTL to 232 and 232 to TTL two different products (essentially, two different line sequences are defined). Emphasize that the conversion of TTL/232 is two-way, and there is no one-way. Conversion, the so-called one-way conversion is a misunderstanding.
2. RS-232 level is not suitable for too high communication rate, the highest stable speed is about 460800bps (some are not good quality can only reach 115200bps), no matter how high it is, it is not stable (higher rate is recommended to use TTL level Communication).
Model Description:
Both provide PCB package library and principle library in Altium format for easy integration into your own products.
●Single-channel model: MCS-51A, volume 15*20mm
●Two-way model: MCS-51B, volume 16*20mm
●Single channel with indicator light: MCS-51A LED, volume 12*33mm
●Dual-channel with indicator light: MCS-51B LED, volume 16*33mm
main feature
● Original imported SP3232 chip, original Samsung capacitor, brand new material, stable speed can reach 460800bps (4 times of 115200)
● Support 1 channel/2 channel serial communication at the same time (can also be used as hardware flow control CTS/RTS control pin when not in use).
●3.0-5.5V wide voltage range, adapt to different voltage systems (TTL side signal level cannot be higher than power supply level)
●Mini size 20*16*3mm, standard 2.54mm pitch. Very suitable for integration into products.
● Provide Altium Designer package files to simplify design work.
A brief description of some common technical issues:
This description introduces some basic concepts of serial communication for reference
UART:
Universal Asynchronous Receiver/Transmitter, usually called UART, is essentially a serial communication protocol. Generally speaking, the serial port is UART.
COM:
The COM port (cluster communication port) is the serial communication port, referred to as the serial port. Generally, in the Windows computer device manager, the serial port is displayed as a COM port.
COM and UART are the same protocol. They are often called COM on the computer side and UART on the MCU side.
Note: UART and COM are both communication protocols, not level standards, nor interface forms.
TTL:
TTL is the abbreviation of "Transistor-Transistor Logic". High level is equivalent to logic "1", and 0V is equivalent to logic "0".
In serial communication, TTL is regarded as shorthand for TTL UART.
RS-232:
RS is the abbreviation of "Recommend Standard" in English, and 232 is the identification number. Use negative logic level, logic 1=-3V～-15V, logic 0=+3～+15V
Note: TTL and RS-232 are both level standards, not encoding protocols, nor interface forms. TTL level and RS-232 level cannot be directly connected, so a conversion circuit is required.
TTL to 232:
TTL level UART signal is converted to RS-232 level UART signal (only hardware level conversion, no communication protocol involved)
DR9/DB9:
A 9-pin interface, commonly found on older desktop computer motherboards, used for serial communication. Normally, the DR9/DB9 interface is RS-232 level (except for special instructions). At present, mainstream motherboards generally have only one serial port or even no serial port. Therefore, the USB-to-serial circuit is commonly used.
VCC:
Generally refers to the positive input terminal of the power supply. . GND: Generally refers to the negative input terminal of the power supply. When different circuits are connected to each other, GND should be connected, but VCC is not necessarily.
The meaning of flow control RTS and CTS in UART communication
The following content is for reference only. Customers who don't need flow control can ignore it, which will not affect communication at all.
1. Flow control, as the name implies, means flow control. The purpose is to coordinate the sending and receiving parties so that data will not be lost.
2. Many people have used the serial port for a long time and don't know this. This is because it is really unnecessary in many occasions. The baud rate of the sender and receiver is fixed, and the receiving array is large enough. At this time, there will be no data loss caused by the receiver receiving the array overflow. The main purpose of using flow control is when the amount of data is large, and the receiving array may overflow. A measure taken to coordinate the sending and receiving parties.
3. The flow control is designed to two ports, RTS and CTS, and both sender and receiver have their own RTS and CTS, such as communication parties A and B. Then the RTS of A is connected to the CTS of B, and the CTS of A is connected to the RTS of B.
The function of RTS is to tell the other party that I can accept data, which is an output port; the function of CTS is to control sending or not generating data according to the level.
For example: A communicates with B, and now A sends data to B. When B has a certain situation (maybe the receiving buffer is almost full), B's RTS is pulled down (usually pulled down to indicate effective, but not necessarily), A's CTS is connected to B's RTS, and A detects that its CTS is pulled down, knowing that B is telling him not to send any more, and he stops sending. When B can continue to receive data, B's RTS is pulled high, and A's CTS is also pulled high at this time, and A knows that it can continue to send data. It is the same if the receiving and sending situation of A and B are changed.
4. The above is the flow control of the hardware. The receiver informs or controls the sending of the sender through the level of the pin. This method is tried regardless of whether the data sent is in binary format or character format.
In addition, software flow control is the opposite of hardware flow control. Software flow control does not need the RTS and CTS pins. When the receiver does not want to continue to receive data, it sends an XOFF signal to the sender through the receiver’s TXD, and the sender stops sending data after receiving this character; wait until the receiver When it can continue to receive data, the receiver sends an XON signal to the sender, and the sender continues to send data. Because the XON and XOFF signals are also sent through the data signal line, errors may occur when the software flow control transmits binary data, because there may be binary values corresponding to XON and XOFF in the data you send. But this situation can also be resolved, such as escaping XON and XOFF.
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