Source Edit

74HC595 Shift Register Module - 8-bit Serial-to-Parallel Output

Device driver for CD74HC595 8-bit shift register (output expander). Supports daisy-chaining up to 16 devices.

Hardware: CD74HC595 8-bit serial-to-parallel shift register Interface: 3-wire serial (LATCH, CLK, DATA) Supply: 2V-6V (3.3V compatible) Features:

Up to 16 devices can be daisy-chained (128 outputs)
High-current outputs (6mA at 5V)
Tri-state outputs (when OE is HIGH)

Pin Connections:

Pin 11 (SRCLK) → CLK (shift register clock)
Pin 12 (RCLK) → LATCH (storage register clock)
Pin 14 (SER) → DATA (serial data input)
Pin 13 (OE) → GND (output enable, active LOW)
Pin 10 (SRCLR) → 3.3V (shift register clear, active LOW)

Daisy Chaining: Connect QH' (pin 9) of first device to SER (pin 14) of next device.

Example:

import nimphea
import nimphea/dev/sr595

var sr: ShiftRegister595
var pins = [newPin(PORTB, 0),  # LATCH
            newPin(PORTB, 1),  # CLK
            newPin(PORTB, 2)]  # DATA

sr.init(addr pins[0], 2)  # 2 devices daisy-chained (16 outputs)

sr.set(0, true)   # Set output QA on first device HIGH
sr.set(15, true)  # Set output QH on second device HIGH
sr.write()        # Shift out the data

Imports

nimphea

Types

ShiftRegister595 {.importcpp: "daisy::ShiftRegister595", bycopy.} = object: Source Edit
ShiftRegister595Pins {.importcpp: "daisy::ShiftRegister595::Pins", size: 4.} = enum PIN_LATCH = 0, ## LATCH corresponds to Pin 12 "RCLK" PIN_CLK = 1, ## CLK corresponds to Pin 11 "SRCLK" PIN_DATA = 2, ## DATA corresponds to Pin 14 "SER" NUM_PINS = 3: Source Edit

Consts

kMaxSr595DaisyChain = 16: Source Edit

Procs

proc init(sr: var ShiftRegister595; pin_cfg: ptr Pin; num_daisy_chained: csize_t = 1) {....raises: [], tags: [], forbids: [].}: Initialize shift register(s)

Parameters:

pin_cfg: Array of 3 pins LATCH, CLK, DATA

num_daisy_chained: Number of devices (1-16, default 1)

Pin Order:

pin_cfg0 = LATCH (Pin 12 RCLK)

pin_cfg1 = CLK (Pin 11 SRCLK)

pin_cfg2 = DATA (Pin 14 SER)

Source Edit
proc set(sr: var ShiftRegister595; idx: uint8; state: bool) {....raises: [], tags: [], forbids: [].}: Set the state of a specific output

Parameters:

idx: Output index (0-127 depending on daisy chain length)
Device 1: QA=0, QB=1, ..., QH=7

Device 2: QA=8, QB=9, ..., QH=15

etc.

state: true = HIGH, false = LOW

Note: Call write() to shift the data out to the hardware
Source Edit
proc write(sr: var ShiftRegister595) {....raises: [], tags: [], forbids: [].}: Shift out all buffered data to the shift register(s)

This latches the data to the output pins. Call this after setting all desired outputs with set().
Source Edit