Chain Key UART Control Protocol (Documentation V1)

1. Basic Information

2. Data Frame Format

All packets start with 0xAA 0x55 and end with 0x55 0xAA. Multi-byte length fields are entered low byte first.

2.1 Request Frame Format

Request Frame:
  AA 55 <Length_low> <Length_high> <Index> <Cmd> <Req Data...> <CRC> 55 AA

2.2 Response Frame Format

Response Frame:
  AA 55 <Length_low> <Length_high> <Index> <Cmd> <Resp Data...> <CRC> 55 AA

2.3 Response Data Convention

3. Checksum

CRC = (Index + Cmd + Data[0] + ... + Data[n]) & 0xFF

3.1 Checksum Example

#include <stddef.h>
#include <stdint.h>

uint8_t chain_calc_crc(uint8_t index, uint8_t cmd,
                       const uint8_t *data, size_t data_len)
{
    uint16_t sum = index + cmd;

    for (size_t i = 0; i < data_len; i++) {
        sum += data[i];
    }

    return (uint8_t)(sum & 0xFF);
}

4. Quick overview of commands

5. Command Details

5.1 Set RGB value - Cmd 0x20

Request data

Input parameters: Index_id (device index ID), Index (starting coordinates of the RGB lamp), Num (number of RGB to be set), RGB value

Request Frame:
  AA 55 | 0x05+Num*3 | 0x00 | Index_id | 0x20 | Index | Num | R | G | B | ... | CRC | 55 AA

Response Data

Return parameters: Operation_status

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | 0x20 | Operation_status | CRC | 55 AA

Things to note

1. Operation_status operation status
   • 0: Operation failed
   • 1: Operation successful
2. Index is the starting coordinate of the RGB light, starting from 0. The Key device has two RGB lights. By definition, the two RGB lights are of the same color, so Index = 0, Num = 1

5.2 Get RGB value - Cmd 0x21

Request data

Input parameters: Index_id (device index ID), Index (starting coordinates of RGB lights), Num (number of RGB lights to be read)

Request Frame:
  AA 55 | 0x05 | 0x00 | Index_id | 0x21 | Index | Num | CRC | 55 AA

Response Data

Return parameter: RGB value

Response Frame:
  AA 55 | 0x04+Num*3/0x04 | 0x00 | Index_id | 0x21 | Operation_status | R | G | B | ... | CRC | 55 AA

Things to note

1. Operation_status operation status
   • 0: Operation failed
   • 1: Operation successful
2. Index is the starting coordinate of the RGB light, starting from 0. The Key device has two RGB lights. By definition, the two RGB lights are of the same color, so Index = 0, Num = 1
3. The operation failed and the returned data packet did not contain RGB values.

5.3 Set RGB light brightness - Cmd 0x22

Request data

Input parameters: Index_id (device index ID), Light (RGB brightness, 0~100, default 40), Save_to_flash (whether to save to internal Flash)

Request Frame:
  AA 55 | 0x05 | 0x00 | Index_id | 0x22 | Light | Save_to_flash | CRC | 55 AA

Response Data

Return parameters: Operation_status

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | 0x22 | Operation_status | CRC | 55 AA

Things to note

1. Operation_status operation status
   • 0: Operation failed
   • 1: Operation successful
2. Save_to_flash Whether to save internal Flash
   • 0: Do not save
   • 1：Save
3. Successful setting takes effect immediately
4. Saving to the internal Flash requires erasing the page, which is a time-consuming process (about 20ms). During this period, the serial port interrupt will be turned off, and frequent operations will affect the life of the device. If you need to adjust the brightness frequently, please avoid saving to the internal Flash every time.

5.4 Get RGB light brightness - Cmd 0x23

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | 0x23 | CRC | 55 AA

Response Data

Return parameters: Light (RGB brightness)

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | 0x23 | Light | CRC | 55 AA

Things to note

5.5 chain device presses, actively sends - Cmd 0xE0

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  Device-initiated report，No host request frame

Response Data

Return parameters: Status (key trigger status)

Response Frame:
  Device-initiated report，No response frame

Things to note

1. Status button status
   • 0: click
   • 1: Double click
   • 2: long press
2. This packet is only sent in active reporting mode. After the data packet is sent, the RGB light will superimpose the effect on the light effect set by the user: • Click on Overlay Green (G) • Double click to overlay blue (B) • Long press to overlay red (R) The color channel value of each overlay is 255, and gradually decays with a 10ms cycle within 1 second. The final overlay value drops to 0 and returns to the color effect set by the user. Example: The user sets the RGB light to purple (R=128, G=0, B=128) and the brightness to 50%. After brightness compression, the actual display is: R=64, G=0, B=64. • When the user clicks, the G channel stacks 255: Displayed as R=64, G=255, B=64, the stacked G value gradually decays to 0 over 1 second, and eventually returns to R=64, G=0, B=64. • When the user double-clicks, the B channel superimposes 255: original B=64. After superposition, the value exceeding 255 is processed as 255. After superposition, it is displayed as R=64, G=0, B=255. The superimposed B value gradually decays to 0 within 1 second, and finally returns to R=64, G=0, B=64. • When the user presses and hold, the R channel superimposes 255: original R=64. After superposition, the value exceeding 255 is processed as 255. After superposition, it is displayed as R=255, G=0, B=64. The superimposed R value gradually decays to 0 within 1 second, and finally returns to R=64, G=0, B=64.

5.6 Query button status - Cmd 0xE1

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | E1 | CRC | 55 AA

Response Data

Return parameters: Status

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | E1 | Status | CRC | 55 AA

Things to note

1. Status button status
   • 0: Not pressed
   • 1: Press

5.7 Set key data interval - Cmd 0xE2

Request data

Input parameters: Index_id (device index ID), Double (double-click time interval), Long (long press time interval)

Request Frame:
  AA 55 | 0x05 | 0x00 | Index_id | E2 | Double | Long | CRC | 55 AA

Response Data

Return parameters: Operation_status

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | E2 | Operation_status | CRC | 55 AA

Things to note

1. Double: Double-click time interval (default 1) (Double+1)*100ms 0～9（100ms～1000ms）
2. Long long press time interval (default 0) (Long+3)*1s 0～7（3s～10s）
3. Operation_status operation status
   • 0: Operation failed
   • 1: Operation successful

5.8 Get key data interval - Cmd 0xE3

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | E3 | CRC | 55 AA

Response Data

Return parameters: Double, Long

Response Frame:
  AA 55 | 0x05 | 0x00 | Index_id | E3 | Double | Long | CRC | 55 AA

Things to note

1. Double double-click time interval 0～9 （100ms～100ms）
2. Long long press time interval 0～7（3s～10S）

5.9 Set button mode - Cmd 0xE4

Request data

Input parameters: Index_id (device index ID), Mode (key mode)

Request Frame:
  AA 55 | 0x04 | 0x00 | Index_id | E4 | Mode | CRC | 55 AA

Response Data

Return parameters: Operation_status

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | E4 | Operation_status | CRC | 55 AA

Things to note

1. Mode (default 1)
   • 0: Non-active reporting
   • 1: Take the initiative to report
2. Operation_status operation status
   • 0: Operation failed
   • 1: Operation successful

5.10 Get key mode - Cmd 0xE5

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | E5 | CRC | 55 AA

Response Data

Return parameters: Mode

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | E5 | Mode | CRC | 55 AA

Things to note

1. Mode (default 1)
   • 0: Non-active reporting
   • 1: Take the initiative to report

5.11 Query the unique UID of the device - Cmd 0xF8

Request data

Input parameters: Index_id (device index ID), UID_Type

Request Frame:
  AA 55 | 0x04 | 0x00 | Index_id | 0xF8 | UID_Type | CRC | 55 AA

Response Data

Return parameters: Operation_status, UID

Response Frame:
  AA 55 | 0x04+4/12 | 0x00 | Index_id | 0xF8 | Operation_status | UID (multi-byte) | CRC | 55 AA

Things to note

1. Operation_status operation status
   • 0: Operation failed
   • 1: Operation successful
2. UID_Type UID type
   • 0：4byte UID
   • 1：12byte UID

5.12 Query the upgrade program version number - Cmd 0xF9

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | 0xF9 | CRC | 55 AA

Response Data

Return parameters: Bootloader_version

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | 0xF9 | Bootloader_version | CRC | 55 AA

Things to note

5.13 Query the device software version number - Cmd 0xFA

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | 0xFA | CRC | 55 AA

Response Data

Return parameters: Firmware_version

Response Frame:
  AA 55 | 0x04 | 0x00 | Index_id | 0xFA | Firmware_version | CRC | 55 AA

Things to note

5.14 Query device type - Cmd 0xFB

Request data

Input parameter: Index_id (device index ID)

Request Frame:
  AA 55 | 0x03 | 0x00 | Index_id | 0xFB | CRC | 55 AA

Response Data

Return parameters: Device_type

Response Frame:
  AA 55 | 0x05 | 0x00 | Index_id | 0xFB | Device_type_low | Device_type_high | CRC | 55 AA

Things to note

1. Device_type = (uint16_t)((Device_type_high << 8) | Device_type_low)
2. The device type code of Key is 0x0003

5.15 Enumeration request, sent by the end device of chain link change, and sent by the device when it is powered on, notifying the host to update the link device status - Cmd 0xFC

Request data

Input parameters: none

Request Frame:
  Device-initiated report，No host request frame

Response Data

Return parameters: none

Response Frame:
  Device-initiated report，No response frame

Things to note

None.

5.16 Heartbeat packets, regular communication between chain devices, can self-discover whether they are end devices, and the host can also use heartbeat packets to determine whether there is a chain device connection - Cmd 0xFD

Request data

Input parameters: none

Request Frame:
  AA 55 | 0x03 | 0x00 | 0xFF | 0xFD | CRC | 55 AA

Response Data

Return parameters: none

Response Frame:
  AA 55 | 0x03 | 0x00 | 0xFF | 0xFD | CRC | 55 AA

Things to note

5.17 Enumerate to obtain the number of cascaded devices - Cmd 0xFE

Request data

Input parameter: Send_num (default 0, used to record the number of devices)

Request Frame:
  AA 55 | 0x04 | 0x00 | 0xFF | 0xFE | Send_num | CRC | 55 AA

Response Data

Return parameter: Receive_num (the value represents the number of devices)

Response Frame:
  AA 55 | 0x04 | 0x00 | 0xFF | 0xFE | Receive_num | CRC | 55 AA

Things to note

None.

6. Status code/enumeration value

6.1 Operating status

Other modes, ranges, and event enumeration values are defined in the "Notes" of the corresponding instructions.

7. Version records