PF reading is wrong with C library.

By ayush , 27 May, 2021

Forums

Hi,
When i am decoding PF value with the C libraray its giving wrong value, but the same response if I am decoding in the DLMS translator its showing correct there. Can you pls tell me why its happening below is the data.

cmd: 7e a0 1a 02 a1 21 32 a2 cb e6 e6 00 c0 01 81 00 03 01 01 49 07 00 ff 02 00 97 73 7e
Response: 7e a0 13 21 02 a1 52 21 3f e6 e7 00 c4 01 81 00 0f aa 7d 5e 7e
Received data 1.1.73.7.0.255 , 2:
Value : 170 (actual data is -86)
Value in HEX: aa

cmd:7e a0 1a 02 a1 21 54 92 cd e6 e6 00 c0 01 81 00 03 01 01 49 07 00 ff 03 00 4f 6a 7e
Response: 7e a0 17 21 02 a1 74 05 56 e6 e7 00 c4 01 81 00 02 02 0f fe 16 ff 38 db 7e
Scaler : -2

Converted value : 1.70

Thank you.

Hi can you please update on

Hi can you please update on this please.

Hi,

You are reading different attributes. In the first command, you are reading attribute #2 (Value) and in the second you are reading attribute #3 (Scaler and unit).

Read the same attribute index and the values are the same.
BR,
Mikko

Hi,

Hi,
Thanks for your reply. If you see the below data its coming proper for other PF. As per my observation whenever PF is in -ve value that time only this wrong conversion is happening from the resp.

cmd : 7e a0 1a 02 a1 21 fe c2 c7 e6 e6 00 c0 01 81 00 03 01 01 35 07 00 ff 02 00 62 87 7e
Resp: 7e a0 13 21 02 a1 1e 49 b7 e6 e7 00 c4 01 81 00 11 26 98 1f 7e
Value : 38
Value in HEX: 26

cmd: 7e a0 1a 02 a1 21 10 b2 c9 e6 e6 00 c0 01 81 00 03 01 01 35 07 00 ff 03 00 ba 9e 7e
resp: 7E A0 17 21 02 A1 30 25 52 E6 E7 00 C4 01 81 00 02 02 0F FE 16 FF 38 DB 7E
Scaler : -2

Converted Value : o.38

Hi,

ANSI C doesn't multiply the value with scaler for you. You must do it by yourself. The reason is that memory footprint is kept as small as possible.

BR,
Mikko

Hi,

Hi,
I think we are getting confused with the topic of conversation. I will start once again from the top to clarify my doubt.

cmd: 7e a0 1a 02 a1 21 32 a2 cb e6 e6 00 c0 01 81 00 03 01 01 49 07 00 ff 02 00 97 73 7e
Response: 7e a0 13 21 02 a1 52 21 3f e6 e7 00 c4 01 81 00 0f aa 7d 5e 7e

Above are the command and responses to collect one of the Power factor from the meter with OBIS 1.1.73.7.0.255.
In the meter display power factor for this particular OBIS is coming as "-0.86", but from the DLMS library after converting the response command (7e a0 13 21 02 a1 52 21 3f e6 e7 00 c4 01 81 00 0f aa 7d 5e 7e) the value is coming as "170" instead of "-86" in reg.value.lVal.

This is happening only when there is a negative power factor.
We are using the same DLMS library which has been purchased from Gurux.

Please clarify where this conversion is happening in DLMS library and how can we make it convert properly.

below is the code snippet for your reference.
if (requestType == DLMS_OBJECT_TYPE_REGISTER)
{
delay_us(100);
queryStatus = com_read(&con, &reg.base, 2);
if(queryStatus == 0)
{
debug_print("\r\nReceived data %s , 2: ",dlmsDevice->oidList.oid[oididx]);
debug_print("\r\nValue : %d\r\n",reg.value.lVal); // Here its coming 170 instead of -86
for(pIdx=0;pIdx<con.data.size;pIdx++)
{
debug_print("%02X ",con.data.data[pIdx]);
}
debug_puts("\n");
}

if(queryStatus == 0)
{
queryStatus1 = com_read(&con, &reg.base, 3);
if(queryStatus1 == 0)
{
debug_print("\r\nReceived data %s , 3: ",dlmsDevice->oidList.oid[oididx]);
debug_print("\r\nScaler : %d\r\n",reg.scaler);
for(pIdx=0;pIdx<con.data.size;pIdx++)
{
debug_print("%02X ",con.data.data[pIdx]);
}
debug_puts("\n");
}
}
}