DALI - DT8 - CCT Control command

Question

I made the below code for setting CCT in DALI DT8 drivers as per the discussion on DALI 209 - Device Type 8 - CCT control and DALI DT6-DT8 Sending commands above 255 The DTR setting is working perfectly and I can read back the DTR value using query commands but the CCT is not setting at all.

CODE:

    void Dali::setCCT(uint8_t id, long kelvin)

{

    if (id < 64 && kelvin <= 6500 && kelvin >= 2000)
    {

        uint8_t val1 = (1000000 / kelvin) / 256;
        uint8_t val2 = (1000000 / kelvin) - (val1 * 256);
        dali.setDTR0(val1);  ///set val1 as DTR0
        delay(10);
        dali.setDTR1(val2);   ///set val2 as DTR1
        delay(10);
        dali.enabledt8();    ///enable DT8
        delay(10);
        dali.transmit((id * 2) + 1, 231);  ///set temp color temperature
    }
}

I checked all the available documents and even tried sending the command twice (since some of the commands should be sent twice) but no result.

what am I doing wrong here?

Answer 1

In the code given,

val1 is the MSB of the Mirek value, since it is is the value / 256.

val2 is the LSB of the Mirek value, since it is value - MSB * 256.

Table 15 in IEC62386-209 shows which DTRs are used for which commands.

So the commands, including command 231 which you are using, pick up their colour from DTR1 as MSB and DTR0 as LSB. But you are sending the MSB (your val1) as DTR0 and LSB (your val2) as DTR1.

So when you try to send a colour of say 200 Mirek (MSB=0, LSB=200) you are actually sending (MSB=200, LSB=0) which is 200*256+0 = 51200 which is out of range (50 to 1000 is the valid range) so the gear ignores it.