/ni2c

The NI2C is an universal i2c nixie driver

Primary LanguageC++OtherNOASSERTION

Nixie i2c Driver

This simple, custom nixie driver is indented to drive any kind of nixie tubes via i2c interface. It allows to address two tubes with each i2c slave. The module is intended to be stackable and dynamically addressable using dip switches.

  • Supports up to 8 stacked drivers
  • Each driver module can power 2 nixie tubes

The driver module has been tested with the following nixie tubes:

  • IN-4
  • IN-7

BOM - Bill of Materials

Name Count Component Description
74141 2x SN74141 or K155ID1 BCD decoder
PCF8574 1x PCF8574 i2c I/O expander
SW1/SW2 1x DIP Switch 4
R1, R2 2x 10kΩ Resistor bus pull-up
R3, R4, R5, R8 4x 10kΩ Resistor
R6, R7 2x 10kΩ 2W Resistor
C2, C3, C4 3x 0.1µF Capacitor optional
STACK PWR 1x pin-2 Male/female pin header use male header with long pins to stack the module. Use a short pinned header for the bottom module
HV PWR 1x pin-2 Male/female pin header use male header with long pins to stack the module. Use a short pinned header for the bottom module
PWR 1x screw terminal optional, power can also be supplied via STACK PWR
I2C 1x pin-2 Male/female pin header i2c bus, 1:SDA 2:SCL
NX1, NX2 2x pin-8 Male pin header 90° angle for stackable module
ANODE 1x pin-6 Male pin header 90° angle for stackable module

Schema

description

Assembly instructions

  • The capacitors are optional as they're used as bypass

Problem Solving

  • If the tubes don't light up correctly you might have to change R6, R7. You can use this calculator to determine the resistor values based on the HV power supply

I2c Interface Definition

Byte 7(MSB) 6 5 4 3 2 1 0(LSB)
i2c slave address L H H H A2 A1 A0 R/W
I/O data bus P7 P6 P5 P4 P3 P2 P1 P0

Address Reference

  • Only the write addresses are shown as the nixie driver module doesn't support read operations.
  • Arduino uses 7-bit addresses, the LSB (R/W) is not set and the address range starts at 0x38
A2 A1 A0 i2c bus 8-bit slave address
L L L 0x70
L L H 0x72
L H L 0x74
L H H 0x76
H L L 0x78
H L H 0x7A
H H L 0x7C
H H H 0x7E

BCD Decoder Reference

The two bcd decoders each use 4-bit of the 8-bit I/O expander.

The 74141 decoder has 4 inputs marked A,B,C,D which trigger corresponding outputs.

Truth Table

D C B A Output
L L L L 0
L L L H 1
L L H L 2
L L H H 3
L H L L 4
L H L H 5
L H H L 6
L H H H 7
H L L L 8
H L L H 9

All values above 0x9 are out of range and turn all outputs off.

  • "on" range: 0x0..0x9
  • "off" range: 0xA..0xF

Using the Nixie i2c module

Based on the logic tables of the bcd decoders, writing to the i2c bus to output numbers is quite simple.

One byte defines the values for both decoders:

Decoder Bits
NIXIE 1 0000ABCD
NIXIE 2 ABCD0000

Data Examples

Example value Nixie Output
0xFF all off
0x12 "21"
0x01 "10"