Distorted Signal Transmission RawCAN
8 years 3 months ago - 8 years 3 months ago #29530653
by Trainee
Distorted Signal Transmission RawCAN was created by Trainee
Hello,
I have a HBL1650. I am using RawCAN mode to send CAN frames to computer for data acquisition purpose. I first generated a sinusoidal signal of 2Hz, with 2V peak to peak amplitude and wired the signal into one of the analog input of the controller HBL1650. I then wrote a RawCAN microBasic script to read the sinusoidal signal and send the value in a CAN frame.
The problem is after I have acquired the CAN frame and done some calculation from the 8 bytes of the CAN frame to extract the value of the sinusoidal signal, I saw that the signal is distorted.
Below is my RawCAN script:
I have attached an image of the signal that I got after being transmitted through CAN bus.
I have tried adding a "print(time,";",anain1,";",reste_anain1,";",anain2,"\n")" line into the code and copied the result from Roborun console page into the text to see if the signal is distorted. It wasn't. But when it was transmitted through CAN bus, the signal wasn't the same as the original. There is an offset on the signal.
The weird thing is when I change the line "anain1=getvalue(_ANAIN,1)" to "anain1=2536", which is a fixed value, I got a the same value of 2536 even after being transmitted through CAN bus. So I assume that the error doesn't come from the CAN bus. But I don't know where does the error come from.
CAN anyone explain to me where does the error come from please?
I have a HBL1650. I am using RawCAN mode to send CAN frames to computer for data acquisition purpose. I first generated a sinusoidal signal of 2Hz, with 2V peak to peak amplitude and wired the signal into one of the analog input of the controller HBL1650. I then wrote a RawCAN microBasic script to read the sinusoidal signal and send the value in a CAN frame.
The problem is after I have acquired the CAN frame and done some calculation from the 8 bytes of the CAN frame to extract the value of the sinusoidal signal, I saw that the signal is distorted.
Below is my RawCAN script:
top:
pending = GetValue(_CF) 'check if any frames are present in the 16-trames FIFO buffer
canID = GetValue(_CAN, 1) 'get the ID of the CAN frame received
if pending <> 0 then 'if CAN frame present then
'Read
canDataLength = getValue(_CAN, 2) 'get the length of CAN frame (number of bytes)
canData1 = getValue(_CAN, 3) 'get byte 1
canData2 = getValue(_CAN, 4) 'get byte 2
canData3 = getValue(_CAN, 5) 'get byte 3
canData4 = getValue(_CAN, 6) 'get byte 4
canData5 = getValue(_CAN, 7) 'get byte 5
canData6 = getValue(_CAN, 8) 'get byte 6
canData7 = getValue(_CAN, 9) 'get byte 7
canData8 = getValue(_CAN, 10) 'get byte 8
end if
setCommand(_CANSEND, 1, canID)
time=getvalue(_TM,1)
anain1=getvalue(_ANAIN,1)
reste_anain1=anain1 mod 256
anain2=anain1/256
setCommand(_CANSEND, 3, reste_anain1)
setCommand(_CANSEND, 4, anain2)
setCommand(_CANSEND, 5, time)
setCommand(_CANSEND, 6, 0)
setCommand(_CANSEND, 7, 0)
setCommand(_CANSEND, 8, 0)
setCommand(_CANSEND, 9, 0)
setCommand(_CANSEND, 10, 0)
setCommand(_CANSEND, 2, canDataLength)
wait(1)
goto topI have attached an image of the signal that I got after being transmitted through CAN bus.
I have tried adding a "print(time,";",anain1,";",reste_anain1,";",anain2,"\n")" line into the code and copied the result from Roborun console page into the text to see if the signal is distorted. It wasn't. But when it was transmitted through CAN bus, the signal wasn't the same as the original. There is an offset on the signal.
The weird thing is when I change the line "anain1=getvalue(_ANAIN,1)" to "anain1=2536", which is a fixed value, I got a the same value of 2536 even after being transmitted through CAN bus. So I assume that the error doesn't come from the CAN bus. But I don't know where does the error come from.
CAN anyone explain to me where does the error come from please?
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