Nixie i2c driver
- Supports up to 8 stacked drivers
- Each driver module can power 2 nixie tubes
Introduction
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" |
