CH376 USB Development Board Evaluation Board

DESCRIPTION:

Crystal X1 is a standard 12MHz, USB host USB device is higher than the required frequency accuracy, X1 error requirement is less than 0.4 ‰, ordinary 12MHz crystal basically meet the requirements. It is strongly recommended to shorten the length of the relevant lead to reduce interference.

Capacitor C4 for internal power supply decoupling node to reduce transmission during USB EMI, 4700pF to 0.1uF, you can use an ordinary chip capacitors 103 0.01uF.

P4 is a USB port can be used either USB HOST host mode, the device can also be used for USB DEVICE mode, resistor R1 is used to limit the output current to an external USB device, to avoid power supply voltage when U disk and other USB devices just inserted short-term decline, or even cause abnormal CH376 or microcontroller reset or internal RAM data errors. If a USB external hard drive, you should replace the DC resistance of the resistor R1 is smaller inductor, or alternatively use a 5V power supply provides greater direct operating current (500mA or more) to an external hard drive. In addition, the capacity of the power supply decoupling capacitor C9 of USB-HOST socket can not be too small, some large capacity (should be greater than 100μF) can reduce the power supply voltage fluctuations in the USB device just inserted.

P5 is the SD card socket, can reach the size of a standard SD card, the other specifications of the SD card may need to convert additional seat. Resistor R3 is used to limit the output current to an external SD card, to avoid short-term drop in the supply voltage when the SD card just inserted.

P1 is an 8-bit parallel signal port for necessary signal connected to the microcontroller parallel port, parallel port, including D0-D7, A0, RD #, WR #, CS # and GND, while the INT # is optional.

P2 is a SPI serial signal port for connecting microcontroller SPI interface SPI include the necessary signals SCS, SCK, SDI, SDO and GND, while the INT # is optional.

P3 is an asynchronous serial signal port asynchronous serial port for connection to the microcontroller, the necessary signals include asynchronous serial RXD, TXD and GND, while the INT # is optional. P3 also provides write protection SDWP SD card and plug state SDINSERT signal lines.

Above P1, P2, P3 communications ports can also be supplied from an external 5V power supply to this kit, as well as to the CH376 of RSTI pin provides optional hardware reset signal, if the actual product circuit has μP monitoring circuit, it should be CH376 and microcontrollers with a reset signal. Note that you should try to shorten the length of the signal line between the present and the microcontroller evaluation board no longer than 20cm, otherwise you need to use a special cable signal interval a ground.
J3 is used to select the operating voltage of CH376, shorting 1-2 pin when voltage is 5VWhen shorting 2-3 pin is 3.3V. The default is 5V voltage, but when the MCU operating voltage is equal to or lower than 3.3V, 3.3V voltage can be selected for the CH376. When CH376 chip's operating voltage is 5V, J2 must be disconnected, when CH376 chip's operating voltage is 3.3V, J2 must be shorted.

J1, J5 and J6 for hardware reset after power or select CH376 communication interface with the microcontroller:

If J1 shorted, J5 off, J6 off, then the parallel port is 8;
If J1 off, J5 shorted, J6 shorted, so is the SPI interface;
If J1 off, J5 off, J6 off, then the asynchronous serial port.

Some examples of programs may be using SCM serial output debugging state information, if you need to display the monitoring information may be made after the microcontroller serial RS232 level converter connected to a computer using the serial monitor / debugger software to view. If you are using CH375 evaluation board, it can be connected to a computer serial port J2; if the computer no serial port, or port already occupied by other equipment, it can be transferred by the USB serial chip CH341 provides serial emulation.

CH375 evaluation board inside devices operate at 5V supply voltage, resistance R0 must be added and removed 3.3V regulator D4, work at 3.3V supply voltage, the regulator must be added and removed D4 resistance R0. The default is 5V power supply.