Bus Protocol

16-bit SPI-like protocol at 100kHz between mainboard and control panel.

The Intex PureSpa uses a custom protocol similar to SPI mode 3, but unidirectional for most traffic. Data is inverted, MSB first. Button presses are signaled by pulling the DATA line low at a precise moment.

Signal Overview

DATA

Bidirectional data line (inverted)

CLK

100kHz clock, rising edge samples

HOLD

Chip select, active high

Frame Structure

       |-------------------------------------------------------------------------------|
BIT    | 15 | 14 | 13 | 12 | 11 | 10 |  9 |  8 |  7 |  6 |  5 |  4 |  3 |  2 |  1 |  0 |
       |-------------------------------------------------------------------------------|
CUE    |  0 |  0 |  0 |  0 |  0 |  0 |  0 |  1 |  0 |  0 |  0 |  0 |  0 |  0 |  0 |  0 |
DIGIT  | DP |  x |  A |  B | S3 |  D |  C |  x |  E | S1 | S2 |  G |  F | S4 |  x |  x |
LED    |  0 |  1 |  0 |  x |  0 |  x |  x |  x |  x |  0 |  0 |  0 |  0 |  0 |  0 |  x |
BUTTON |  x |  0 |  x |  x |  0 |  x |  0 |  1 |  0 |  0 |  0 |  0 |  x |  0 |  0 |  0 |
       |-------------------------------------------------------------------------------|

Frame Types

Type	Pattern	Purpose
CUE	0x0100	Frame type separator, sent before each data frame
DIGIT	Has S1-S4 bits	7-segment display data (temperature, time)
LED	Bit 14 set	LED status (power, filter, heater, bubble)
BUTTON	Bit 8 set, others clear	Button scan codes for sending commands

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7-Segment Display

     A
   -----
  |     |
F |     | B
  |     |
   --G--
  |     |
E |     | C
  |     |
   -----
     D      DP

Bits S1, S2, S3, S4 select which of the 4 digits is being addressed.

Frame Cycle

32 frames repeat every 21ms:

C D1 C D2 C D3 C D4 C L
C D1 C D2 C D3 C D4 C L
C D1 C D2 C D3 C D4 C L
C D1 C D2 C D3 C D4 C L
C D1 C D2 C D3 C D4 C L
C B B B B B B B L

C = Cue frame
D1-D4 = Digit frames (4 positions)
L = LED frame
B = Button scan frames (7 for SB-H20)

Button Signaling

Critical Timing

To press a button, the controller must pull the DATA line LOW for 2µs immediately after HOLD goes HIGH, when the matching button scan frame is received.

This must be repeated until the mainboard confirms by sounding the buzzer. The precise 2µs timing is why PIO is essential — WiFi interrupts on ESP8266/ESP32 often disrupt this window.

Button Codes

Button	Code	LED Indicator
Filter	0x0102	0x1000
Heater	0x8100	0x0080
Temp Up	0x1100	—
Temp Down	0x0180	—
Bubble	0x0108	0x0400
Power	0x0500	0x0001
Unit (°C/°F)	0x2100	—

7 of 7 entries

Protocol details from esp8266-intexsbh20 by Jens B. and diyscip by Geoffroy Hubert.