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IO-Jack — PORT Mode

IO jack in PORT mode – digital I/O with 4 bit.

How It Works

In PORT mode, an IO jack reads and writes 4 bit (Pin3 · Pin2 · Pin1 · Pin0).

Every command is a single, composite byte: bit 7 = fixed marker 0, bits 6–4 = command (C2 C1 C0), bits 3–0 = data (Pin3…Pin0):

Bit position 7 6 5 4 3 2 1 0
Field Marker C2 C1 C0 Pin3 Pin2 Pin1 Pin0
0 Command Command Command Data Data Data Data

This gives the operations and the acknowledgment – each as one byte:

Operation 7 6 5 4 3 2 1 0 = Byte
Write – write 4 bit 0 0 0 0 P3 P2 P1 P0 0000 PPPP
Read – read request 0 0 0 1 f f f f 0001 ffff
Read response – 4 bit read 0 0 0 1 P3 P2 P1 P0 0001 PPPP
Set Bit – pins to high 0 0 1 0 M3 M2 M1 M0 0010 MMMM
Clear Bit – pins to low 0 0 1 1 M3 M2 M1 M0 0011 MMMM
Toggle Bit – invert pins 0 1 0 0 M3 M2 M1 M0 0100 MMMM
Return Code – acknowledgment (after write) 0 1 1 1 0 0 0 0 0x70 = No Error
  • P3…P0 = state of Pin3…Pin0 (data nibble, D3…D0)
  • f = read frequencies (data nibble on read): 0 = once, 1–15 = seconds, >16 = milliseconds
  • M3…M0 = bit mask: 1 = pin is changed, 0 = pin stays unchanged
  • Command codes: 000 = Write/Value, 001 = Read, 010 = Set Bit, 011 = Clear Bit, 100 = Toggle Bit, 111 = Return Code

Command Details

All three operations follow the 4-bit data frame 0CCCDDDD (1 byte).

Write — Read/Write Value (Code 0)

0 CCC DDDD  =  0 000 <Pin3 Pin2 Pin1 Pin0>
  • CCC = 000 → command 0 (Read/Write Value)
  • DDDD = the 4 pin states (PAD data)

Read — Read Command (Code 1)

0 CCC DDDD  =  0 001 <Read Frequencies>
  • CCC = 001 → command 1 (Read Command)
  • DDDD = read frequencies: 0 = once, 1–15 = seconds, >16 = milliseconds (periodic reading)
  • The response uses the same read code 001 with the 4 read bits in the data nibble → 0001 PPPP.

Set Bit (Code 2)

0 CCC DDDD  =  0 010 <Bit Mask>
  • CCC = 010 → command 2 (Set Bit)
  • DDDD = bit mask: all pins marked with 1 are set to high, the rest stay unchanged.

Clear Bit (Code 3)

0 CCC DDDD  =  0 011 <Bit Mask>
  • CCC = 011 → command 3 (Clear Bit)
  • DDDD = bit mask: all pins marked with 1 are set to low, the rest stay unchanged.

Toggle Bit (Code 4)

0 CCC DDDD  =  0 100 <Bit Mask>
  • CCC = 100 → command 4 (Toggle Bit)
  • DDDD = bit mask: all pins marked with 1 are inverted, the rest stay unchanged.

Set/Clear/Toggle Bit act selectively via the mask – unlike Write, which always overwrites all 4 pins at once.

Return Code (Code 7)

0 CCC DDDD  =  0 111 0000  =  0x70   → No Error
  • CCC = 111 → command 7 (Return Code)
  • DDDD = 0000 → error code 0 = No Error
Return Code (byte) Meaning
0x70 No Error
0x71 Bad Request
0x72 Not Found
0x73 Request Timeout

More than 4 Pins

The 4-bit frame addresses 4 PADs. For wider ports, the same commands are used in the 8- or 16-bit frame (PAD mask sized accordingly, 8/16 bit).

Port Configuration

For port-wide settings (beyond individual pin operations), there is the Config Port command (code 28, 16-bit frame only) – analogous to Config UART/SPI/I²C. The specific configuration contents are not currently specified.

LED Control

In addition to the pins, the module LEDs can be addressed. This does not use the 4-bit basic pin commands, but its own commands (Set LED code 16, Clear LED code 17, Toggle LED code 18) with a wider frame (16 bit instead of 1 byte):

Code Function Data Effect
16 Set LED LED mask turn on selected LEDs
17 Clear LED LED mask turn off selected LEDs
18 Toggle LED LED mask toggle selected LEDs
  • LED mask: bitfield, one bit per LED (1 = LED is changed, 0 = LED stays unchanged).
  • The LED operations can be used independently of the jack's current operating mode (PORT/I²C/UART/SPI) – unlike the pin commands, which only apply in PORT mode.

Example: LED 1 (red) and LED 2 (green)

Bit position 7 6 5 4 3 2 1 0
LED – – – – – – LED2 (green) LED1 (red)
Action Bit 1 (green) Bit 0 (red) LED mask
Set LED – turn on LED 1 (red) only 0 1 0x01
Set LED – turn on LED 2 (green) only 1 0 0x02
Set LED – turn on both LEDs 1 1 0x03
Clear LED – turn off LED 1 (red) only 0 1 0x01
Toggle LED – toggle both LEDs 1 1 0x03

The LED commands (code 16–18) belong to the same group of 16-bit commands as the config commands (code 25–30) – recognizable by the larger frame, not the 1-byte format of the pin operations.

Transmission: 4 Bytes for 16 Bit of Data

The LED mask is transmitted as a 16-bit data word, but is not sent as 2 raw bytes – the complete command (code + mask) occupies 4 bytes (1 lead byte + 3 continuation bytes), since each byte reserves 2 marker bits for self-synchronization:

Byte Content
0 (lead) Frame marker + command code (high part)
1 Command code (rest) + data bits 15–12
2 Data bits 11–6
3 Data bits 5–0

Complete frames for our example (LED 1 = red, LED 2 = green):

Action LED mask = 4-byte frame
Set LED – LED 1 (red) on 0x0001 E4 80 80 81
Set LED – both LEDs on 0x0003 E4 80 80 83
Clear LED – LED 1 (red) off 0x0001 E4 90 80 81
Toggle LED – toggle both LEDs 0x0003 E4 A0 80 83

Cross References