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Recently, the commissioning program often uses the three serial ports of the single-chip microcomputer to communicate with each other at the same time. I use a USB to TTL serial port debugging module to switch continuously, which not only affects the observation effect, but also makes it laborious.
I planned to purchase 4-channel USB to TTL serial debugging module on Taobao, the average price was 60RMB......
So I decided to DIY a 4-channel USB to TTL serial debugging module~
1. Power supply design
The USB to TTL serial port debugging module needs to convert the computer input 5V into a 3.3V output voltage. The power supply chip uses the XC6206P252MR chip. The XC6206 series is a CMOS step-down with high ripple rejection rate, low power consumption, low dropout, and over-current and short-circuit protection. Type voltage regulator. These devices have very low static bias current, they can provide 250mA output current under the condition of very small input and output voltage difference, and can still maintain a good regulation rate. Because the voltage difference between input and output is small and the static bias current is small, these devices are particularly suitable for battery-powered products that want to extend battery life, such as computers, consumer products, and industrial equipment.
The XC6206P252MR power supply circuit design is as follows:
2. USB hub design
The USB hub chip selects the GL850G-HHY22 chip. GL850G has product features such as low power consumption, low temperature and reduced number of pins. It supports 4 downstream ports (supports 4 USB to TTL communication), and can fully support USB2.0/1.1 specifications, so whether it is a transmission connection with the host side or with other USB device interfaces (high-speed/full-speed/low-speed devices) Transmission) are fully compatible. GL850G also has an overload protection function, provides good EMI/ESD processing, and also provides self-power and bus-power automatic detection modes, so users will not need to re-plug.
Since the hub is a relay station between the host computer and peripheral devices, the market demand for USB hubs has grown substantially in view of the current penetration rate of USB peripheral devices in the market and the popular types of peripheral devices. GL850G can be used in different application fields such as stand-alone hubs, notebook computer docks, or combined with other USB devices to form a USB composite hub. It not only simplifies wiring, but also helps users to manage easily, and can achieve expansion performance. purpose.
GL850G-HHY22 drive circuit design is as follows:
3. USB to TTL design
CH340 is a USB bus adapter chip, which realizes USB to serial port or USB to printer port.
The characteristics of CH340 are as follows:
- Full-speed USB device interface, compatible with USB V2.0.
- Emulate the standard serial port, used to upgrade the original serial peripheral device, or add an additional serial port via USB.
- The serial port application program under the Windows operating system on the computer is fully compatible and does not need to be modified.
- Hardware full-duplex serial port, built-in transceiver buffer, support communication baud rate 50bps～2Mbps.
- Support the commonly used MODEM contact signals RTS, DTR, DCD, RI, DSR, CTS.
- Provide RS232, RS485, RS422 and other interfaces through external level conversion devices.
- CH340R chip supports IrDA standard SIR infrared communication, supporting baud rate from 2400bps to 115200bps.
- Built-in firmware and software compatible with CH341, you can directly use the VCP driver of CH341.
- Support 5V power supply voltage and 3.3V power supply voltage or even 3V power supply voltage.
- CH340C/N/K/E and CH340B have a built-in clock without external crystal oscillator. CH340B also has a built-in EEPROM for serial number configuration.
- Provide SOP-16, SOP-8 and SSOP-20 and ESSOP-10, MSOP-10 lead-free packages, compatible with RoHS.
This project DIY a 4-channel USB to TTL serial port debugging module, so 4 CH340 modules are needed. The circuit design is as follows:
4. Module effect
Since then, the circuit design of a 4-channel USB to TTL serial debugging module has been basically completed (the peripheral interface circuit is relatively simple, so I won’t repeat it here).
The PCB design effect is as follows:
The effect of PCB proofing is as follows:
The communication efficiency is very good~
Purchase link: 30 yuan lower than Taobao market price, only 30RMB can be taken away~
Extended learning: USB2.0 extender (one for four) schematic diagram, PCB, can be used for proofing