The CJMCU164 8-bit shift register board is based on the SN74HC164D IC. The SN74HC164D is an 8-bit serial-in parallel-out shift register.

SN74HC164D

These 8-bit shift registers have AND-gated serial inputs and an asynchronous clear (CLR). The serial inputs (A and B) can be controlled completely; a low level at either input prevents new data from entering and resets the first flip-flop to low at the next clock pulse (CLK). When an input is high, it allows the other to control the first flip-flop's state. Data at the serial inputs can be altered while CLK is high or low, provided the minimum setup time is met. Clocking happens on the low-to-high transition of CLK.

Technical data

• Supply voltage range, Vcc: –0.5 V .. 7 V
• Input clamp current, IiK (Vi < 0 or Vi > Vcc): ±20 mA
• Output clamp current, IoK (Vo < 0 or Vo > Vcc): ±20 mA
• Continuous output current, Io (VO = 0 to Vcc): ±25 mA
• Continuous current through Vcc or GND: ±50 mA

Pin Functions & Usage

• Gated Serial Inputs (DSA/DSB): These two pins are logically AND-gated. To use a single data line from your Arduino, connect one of these pins to 5V and send your data to the other, or simply tie both together.
• No Latch Pin: Unlike the common 74HC595, the '164 lacks a storage/latch register. Data shifted into the register is immediately visible on the output pins (Q0–Q7) as it moves through the register.
• Daisy Chaining: You can connect multiple CJMCU-164 modules by linking the Q7 output of the first module to a serial input (DSA or DSB) of the next

Arduino Pinout

Example Code

This code uses the built-in shiftOut() function to send an 8-bit pattern to the register, which will light up LEDs or drive other parallel components.

// Define pins connected to the CJMCU-164
#define DATA_PIN 2  // Connected to DSA/DSB
#define CLOCK_PIN 3 // Connected to CP
 
void setup() {
  // Set pins as outputs
  pinMode(DATA_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
}
 
void loop() {
  // Example 1: Send a binary pattern (B10101010)
  // This will turn on every other output pin (Q0-Q7)
  shiftOut(DATA_PIN, CLOCK_PIN, LSBFIRST, 0b10101010);
  delay(1000);
 
  // Example 2: "Walking" bit (Light one LED at a time)
  for (int i = 0; i < 8; i++) {
    byte pattern = (1 << i); 
    shiftOut(DATA_PIN, CLOCK_PIN, LSBFIRST, pattern);
    delay(200);
  }
}

Key Technical Details

• No Latch: Because there is no latch (RCLK), the outputs will “flicker” briefly as new data bits are shifted through the register.
• Data Inputs: The board typically has two data inputs (A and B) that are AND-gated. For standard use, tie them together or pull one HIGH and send data to the other.
• Shift Direction: You can use LSBFIRST or MSBFIRST in the shiftOut() function, depending on which output pin (Q0 or Q7) you want to represent the first bit.

https://docs.arduino.cc/tutorials/communication/guide-to-shift-out/

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