Instruction cycle measurement

[Christopher4187]

I assume you are making analog measurements.

Your assumption is wrong.

How do you transfer the data from the PIC to the PC?

I'm a bit confused about your math... You say you need 500Kbs (which is quite a bit), but then you say you want 500 measurements per second. With an ADC resolution of 10 bits (each measurement taking two bytes) that's 1000 bytes per second which would be around 100Kbs. Never the less, the bottleneck is probably in the datatransfer itself.

Is it a continous stream of samples or is it a defined amount of samples at a certain sample rate or what exactly are you trying to do. The 4550 has 2k of ram so depending on what else your program is doing you might be able to store the samples in RAM and then transfer them to the PC - but again, it all depends on what you're doing.

Hi Henrik,

I need to clarify my original post. The 500Kbps is the speed of the CAN network and there are about 500 messages a second. I know the 4550 can do this because the demo boards do it with no problems so it's an issue within my code. Actually, I've seen the demo boards handle 1100 messages a second. Again, I'm not sure if it's the VB code or it's the PIC code. Here is what I have for the PIC code:

START:

RxBuffer = 0                    'clear flag
 
    Low CS
       SSPBUF = %00000011                      'read command
        GoSub letclear
       SSPBUF = CANINTF            'buffer flags are contained in this mcp2515 can controller register
       GoSub letclear
        SSPBUF = 0                  'clock it out
       GoSub letclear
        RXDATA = SSPBUF             'receive buffer status
    High CS
    RxBuffer = RXDATA & %00000011   'isolate last two bits
    If RxBuffer > 0 Then   
                'a buffer is full, or 3, then both are full
        If (RxBuffer = 1) Or (RxBuffer = 3) Then
            RxBufferSub = 1
            DATA35=1                       'VB LED
            GoSub ReceiveCanSub0
        EndIf
        If (RxBuffer = 2) Or (RxBuffer = 3) Then
            RxBufferSub = 2
            DATA35=1                        'VB LED
            GoSub ReceiveCanSub1
        EndIf

GOTO START

ReceiveCanSub0:

LED_RX=0

            Low CS
            SSPBUF = 3               'read
            GoSub letclear
            SSPBUF = RXB0DLC + (RxBufferSub - 1) * 16     'receive buffer of data bytes offset 16
            GoSub letclear
            SSPBUF = 0              'dummy clock it
            GoSub letclear
            RXDATA = SSPBUF         'should contain the number of data bytes
            High CS

            DataBytesRx0 = RXDATA & %00001111  'bits 0-3 contain the number of data bytes 
            DATA1=DATABYTESRX0
            If DataBytesRx0 > 0 Then
                For i = 0 To DataBytesRx0 - 1        '(say data is 2, then 0 and 1)
                 
                    Low CS
                        SSPBUF = 3
                        GoSub letclear
                        SSPBUF = (RXB0D0 + (RxBufferSub - 1) * 16) + i
                        GoSub letclear
                        SSPBUF = 0              'dummy clock
                        GoSub letclear
                        RXDATA = SSPBUF         'mcp2515 can controller data
                    High CS

                    CanDataRx0 [i] = RXDATA
                    DATA2 = CanDataRx0[0] 
                    DATA3 = CANDATARX0[1] 
                    DATA4 = CANDATARX0[2] 
                    DATA5 = CANDATARX0[3] 
                    DATA6 = CANDATARX0[4] 
                    DATA7 = CANDATARX0[5] 
                    DATA8 = CANDATARX0[6] 
                    DATA9 = CANDATARX0[7] 
                Next
            EndIf
            Low CS
                SSPBUF = 3          'read
                GoSub letclear
                SSPBUF = RXB0SIDH + (RxBufferSub - 1) * 16  'high identifier
                GoSub letclear
                SSPBUF = 0          'clock spi
                GoSub letclear
                RXDATA = SSPBUF     'identifier
            High CS

            CanRxIDHigh0 = SSPBUF

            Low CS
                SSPBUF = 3          'read
                GoSub letclear
                SSPBUF = RXB0SIDL + (RxBufferSub - 1) * 16  'low identifier
                GoSub letclear
                SSPBUF = 0          'clock spi
                GoSub letclear
                RXDATA = SSPBUF     'identifier
            High CS

            CanRxIDLow0 = SSPBUF
       
            
            'now, clear the buffer!
            'use bit modify...
                Low CS
                        SSPBUF = %00000101              'bit modify command
                        GoSub letclear
                        SSPBUF = CANINTF                'mcp2515 can controller interrupt flags
                        GoSub letclear
                    SSPBUF = RxBufferSub                'mask for buffer number n
                        GoSub letclear
                        SSPBUF = %00000000              'clock in a clear bit
                        GoSub letclear
                High CS
                LED_RX=1
               DATA35=0                                    'VB LED 
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