RaymondSuTMY / ud-api

UART Packet Format of TMYTEK UD Box

Both Tx/Rx packets follows the format showed above. The packet length is 10 bytes.

Length

The length is counting from frame header to checksum.

Cmd type

0x00

The packet returned from UD Box to denote UD recived “correct” command format.

0x01

Function: Set frequency in kHz resolution

Data payload

• Low byte of target frequency in kHz
• Mid byte of target frequency in kHz
• High byte of target frequency in kHz
• Highest byte of target frequency in kHz
• For the future developed

0x02

Function: Set default frequency

Data payload

• Low byte of target frequency in kHz
• Mid byte of target frequency in kHz
• High byte of target frequency in kHz
• Highest byte of target frequency in kHz
• For the future developed

0xFF

The packet returned from UD Box to denote UD recived “incorrect” command format.

LRC

For every Tx pakcet user needs to prepare LRC checksum before sending the command to UD Box. The LRC is generated by frame header and data payload only.

pseudo code

uint8_t LRC(uint8_t *msgPtr, uint8_t len)
{
  uint8_t mLRC = 0;
  for each element in msgPtr
  {
    mLRC += each element in msgPtr
  }
  return ((uint8_t)(-((uint8_t)mLRC))); // two's complement
}