TPIC6C-PCB

Breakout board for TPIC6C596 shift registers with 8x open drain output with neopixels as status leds.

Features

• Daisy chaining of multiple boards
  • nyanyanyanyanyanyanya
  • "ONE WAY" marks represent the direction, where data goes in and where it comes out
• Neopixel LEDs (WS2812, WS2812B, SK6812 or whatever)
  • Not needed, but nice to have
  • Work independent from the shift registers; only share the same voltage
  • Can be used as output status leds (2x RGBW = 8 bit) or whatever the software wants them to do
  • Can function as signal repeaters to connect a NeoPixel Arcade Button at the end
  • Even if your project is unfinished, it can have nice rainbow animations in an early state
• Main part
  • IC + Basic components
  • 1 Neopixel LED
  • GND, V+ and all 8 Outputs as 2.54 mm pitch THT connector
  • V+ and 5 Outputs (D0 ... D4) as 1.27 mm pitch SMD connector
  • 23 mm x 40.64 mm
  • Connection-Pitch of 35.56 mm
• Extension part
  • Can be cut away if not needed
  • 1 Neopixel LED
    • Or solder jumper for connecting the data line without neopixel
  • GND, V+ and 4 Outputs as 2.54 mm pitch THT connector
  • V+ and 4 Outputs (D4 ... D7) as 1.27 mm pitch SMD connector
  • 2.54 mm screw connector for V+
  • Montage hole
  • Extends PCB to 23 mm x 85.08 mm
  • Connection-Pitch of 80 mm
  • Output connectors 40 mm appart of the main part ones, resulting in output pitch of 40 mm when using D0-D3 on main and D4-D7 on extension part
• Side Connectors
  • Double row connectors
    • Better stability
    • Box headers can be used to connect PCBs over longer distance
    • Can be used to variate the pitch a little
    • Half of outer holes can be cut away to have some kind of plated edge connector, but it doesn't really work for a huge amount of PCBs
  • SPI can be used to set the outputs
    • CLK: SCK
    • D_IN: MOSI
    • SS: Latch
  • Pinout
    • nCLEAR/nCLR (optional)
      • LOW = Reset IC
      • R1 as Pull-Up avialable
    • nOE/nG (optional)
      • LOW = Output Enable
      • R2 as Pull-Down avialable
      • Can be used for PWM dimming
    • Latch/RSCK/SPI_SS
      • Rising Edge: Copy data from shift register to output registers
      • SPI_SS can be used
    • D_IN/SER_IN/SPI_MOSI
      • Data in
      • SPI_MOSI can be used
    • D_OUT/SER_OUT
      • Data out for next shift registers data in
    • CLK/RCK/SPI_SCK
      • Rising Edge: Move data one step forward
      • SPI_SCK can be used
    • 5V/VCC
      • 4.5 ... 5.5 V supply voltage for shift register logic and neopixel
      • Level shifters might be needed for the other input signals
    • GND
      • Ground
    • V+ (optional)
      • 0...33 V
      • Screw terminal can be used for individual V+ on each PCB
      • It's only passed, so it also can be wired external without connecting it to the PCB
    • LED_IN
      • Neopixel Data in
    • LED_OUT
      • Neopixel Data out
• Designed to control (huge amounts of) WERMA signal lamps
  • 24V compatible outputs
  • V+ is X0/COM
  • D0-D7 are outputs for X1, X2, ...
  • GND can be used as always-on output (e. g. for powering a 24V eSIGN or Transceiver)
  • Main part SMD connector features 5 Outputs, because KombiSIGN can handle up to 5 Tiers
  • 40 mm output pitch when using up to 4 outputs, because MC35 has 35 mm diameter and 4 inputs, leaving 5 mm space between lamps
  • 80 mm output pitch when using 5 or more outputs, because eSIGN/KS71/KS72 have 70 mm diameter, leaving 10 mm space between lamps

Known bugs

• Heat transfer
  • Datasheet shows a recommended layout example which isn't in use
  • No problem for me, because I'm far away of these limits
  • Maybe gluing on heatsinks might work
  • Redesign options
    • Implement it
      • Using 4 Layers
      • Increase PCB size
    • Use another IC with better cooling options
    • Add dedicated MOSFETs for higher currents
• Voltage drop on power lines can cause problems on longer chains
  • Voltage drop on V+ only affects the outputs
  • Voltage drop on 5V mostly occurs when using the neopixels on high brightness
  • Voltage drop on GND affects the neopixels and shift registers and is mostly caused by enabled outputs
    • The shift registers glitch if voltage is too low
  • I've ordered the PCBs with only 1 oz Outer Copper Weight
  • I reccomend adding an extra cable for 5V, GND and V+ and connect it regulary
  • Redesign options
    • Add ground plane
    • Increase size of power lines, maybe use both sides of PCB, maybe also increase PCB size to fit everything
    • Order 2 oz Outer Copper Weight
    • Use 4 Layers
    • Pads for connecting cables that run in parallel
    • Use a single box connector for each PCB
      • Most current goes through external ribbon cable
      • Multiple wires for same power lines for less resistance
      • Somehow find an easy way to cut and connect the D_IN/D_OUT and LED_IN/LED_OUT wire correctly
• Missing Resistors/Power-On-Reset
  • Most MCUs have IOs that are inputs on startup and when uploading firmware
  • Open inputs act as antennas
  • Glitches are painful when the outputs are connected to loud buzzers
  • Adding an Pull-Up + IO to nOE helps
  • Redesign options
    • Adding option for Pull-Up on nOE, so outputs are off until the MCU switches this pin to LOW
      • Might cause problems if MCU doesn't run on 5 V and no level shifter is used
      • MCU would need this IO only for start up, if PWM-dimming isn't in use
        • Maybe add solder jumper to latch input; in some cases it's okay to blank all outputs when switching them
    • Adding a simple RC Power-On-Reset to nCLEAR and a Pull-Down to Latch
      • Data in the shift register might glitch, but the controller can fill it with data before latching it to the outputs
      • On power-on, the output registers would be cleared and stay off
      • On firmware upgrades/MCU-reset, the output registers will keep their value
        • Might result in an active buzzer
        • Allows silent/invisible MCU restarts/updates in the background
• Not all WERMA products can operate with V+ as COM
  • I've only had this problem with LED Perm. Beacon WM 24VDC GN/YE/RD
  • At least this board can drive PNP Transistors + Resistors as HIGH-Side-Switches
  • Redesign options
    • Add pads to V+ to add Pull-Up resistors, so P-Channel-MOSFETs can be used as HIGH-Side switches
      • These resistors could also help if LEDs light up dim because of EMC influences on long lines
      • These pads could also function for adding freewheeling diodes when switching inductive loads