Speed of USB EasyHID and Time problem
I'm working on a project measuring high pulse and then during the low pulse, send the value by USB to a VB app.
The problem is that when the period (High and Low pulse) is shorter than aprox 7ms I get strange data from the pic.
I decided to measure how long time a USBOut and USBSERVICE takes and here is what I got:
USBSERVICE = 4.08us
USBOut 8 Byte = 12.4us
USBOut 16 Byte = 15.7us
USBOut 32 Byte = 22.4us
USBOut 64 Byte = 35.7us
So the USB transfer should not affect my measurements of the pulse width.
I use Timer3 to measure parts of my program.
The part of code I measure in the pic code below takes 15.5us.
I use a Basic Stamp to create a squarewave to my pic CCP1 input.
The program looks like this:
In this case I get correct readings sent to the pc.Code:Main: IF IN15 THEN HIGH 6 PAUSE 3 LOW 6 PAUSE 4 ENDIF GOTO Main END
But if I change Pause 4 to Pause 3 the data variates a lot.
Also the Timer3 values in the pic code below variates a lot.
Wich means that that part of code takes different times to execute from time to time.
If I change the Basic Stamp program to this; the data is correct:
And also this works:Code:Main: IF IN15 THEN HIGH 6 PAUSE 0 LOW 6 PAUSE 7 ENDIF GOTO Main END
But as soon the period is under 7ms I get strange values to my vb app.Code:Main: IF IN15 THEN HIGH 6 PAUSE 7 LOW 6 PAUSE 0 ENDIF GOTO Main END
Please help me find what is wrong with my code.
I use a Pic18F4550 20Mhz, MicroCode Studio Plus and Pbp 2.46.
Thanks in advance,
Stefan
Code:'******************************************** 'Pulse width measuring '******************************************** DEFINE OSC 48 DEFINE LOADER_USED 1 DEFINE RESET_ORG 800h ' For Microchip USB Bootloader DEFINE INTERRUPT_ORG 808h ' For Microchip USB Bootloader USBBufferSizeMax con 8 ' maximum buffer size USBBufferSizeTX con 8 ' input USBBufferSizeRX con 8 ' output USBBuffer Var Byte[USBBufferSizeMax] USBBufferCount Var Byte Counts1 Var Word ' Holds Timer1 counts Counts1Of Var Byte ' Holds the Overflow counts Overflow var byte RisingEdge Var Bit Preset Var Bit SendBytes Var Bit SampleNo var byte NewSample var byte CCP1IE var PIE1.2 CCP1IF VAR PIR1.2 TMR1ON VAR T1CON.0 TRM1IF var PIR1.0 TMR1IE VAR PIE1.0 IrOnRising var BYTE IrOnFalling var BYTE x var byte y var byte Led VAR PortB.5 'Timer3 declarations TMR3ON var T3CON.0 TMR3IF var PIR2.1 TMR3IE var PIE2.1 TMR3VALUE var WORD TMR3OverF var byte USBINIT ADCON1 = 15 ' Set PORTA, PORTE and PORTB to digital. TRISD.1 = 0 'Port D Bit 1 as Output TRISB.5 = 0 'Port B Bit6 as Output for LED TRISC.2 = 1 'Port C Bit2 CCP1 as Input IrOnFalling = 4 '0100 = Capture mode: every falling edge IrOnRising = 5 '0101 = Capture mode: every rising edge T1CON.4 = 1 'Timer1 Prescaler Bit4 T1CON.5 = 1 'Timer1 Prescaler Bit5 Counts1 = 0 TMR1H = 0 TMR1L = 0 CCP1CON = IrOnRising '0101 = Capture mode: every rising edge CCP1IE = 1 'CCP1IE Interrupt Disabled SampleNo = 1 Counts1Of = 0 Overflow = 0 Low Led 'Timer3 inits TMR3OverF = 0 TMR3IE = 1 TMR3IF = 0 T3CON.4 = 0 T3CON.5 = 0 ProgramStart: USBSERVICE ' keep connection alive if TRM1IF THEN 'If Timer1 Overflows Overflow = Overflow + 1 'Incr Overflow counter TRM1IF = 0 'Reset Flag ENDIF IF CCP1IF = 0 THEN ProgramStart 'Return if no Interrupt IF CCP1CON = IrOnRising THEN CCP1IF = 0 'Reset Flag CCP1IE = 0 'CCP1IE Interrupt Disabled CCP1CON = IrOnFalling 'Capture mode: every falling edge CCP1IE = 1 'CCP1IE Interrupt Enabled TMR1H = 0 TMR1L = 0 TMR1IE = 1 'Enable overflow flag TMR1ON = 1 'Start Timer 1 ' high Led goto ProgramStart ENDIF IF CCP1CON = IrOnFalling THEN TMR3ON = 1 'Using Timer3 for measuring CCP1IF = 0 'Reset Flag Counts1.HighByte = CCPR1H 'Save Values Counts1.LowByte = CCPR1L Counts1Of = Overflow Overflow = 0 'Reset Overflow counter CCP1IE = 0 'CCP1IE Interrupt Disabled CCP1CON = IrOnRising 'Capture mode: every rising edge CCP1IE = 1 'CCP1IE Interrupt Disabled 'TMR1ON = 0 'Stop Timer 1 TMR1H = 0 TMR1L = 0 if SampleNo = 1 then 'SampleNo used by VB app. SampleNo = 2 else SampleNo = 1 endif USBBuffer(0) = Counts1.LowByte Counts1.LowByte = 0 USBBuffer(1) = Counts1.HighByte Counts1.HighByte = 0 USBBuffer(2) = Counts1Of USBBuffer(3) = SampleNo USBBuffer(4) = TMR3VALUE.highbyte USBBuffer(5) = TMR3VALUE.lowbyte 'low Led Gosub DoUSBOut TMR3ON = 0 'Using Timer3 for measuring TMR3VALUE.highbyte = TMR3H TMR3VALUE.lowbyte = TMR3L TMR3H = 0 TMR3L = 0 goto ProgramStart ENDIF GOTO ProgramStart ' ************************************************************ ' * receive data from the USB bus * ' ************************************************************ DoUSBIn: USBBufferCount = USBBufferSizeRX ' RX buffer size x=x+1 if x > y THEN Skipping USBService ' keep connection alive USBIn 1, USBBuffer, USBBufferCount, DoUSBIn ' read data, if available Skipping: x=0 return ' ************************************************************ ' * wait for USB interface to attach * ' ************************************************************ DoUSBOut: USBBufferCount = USBBufferSizeTX ' TX buffer size USBService ' keep connection alive USBOut 1, USBBuffer, USBBufferCount, DoUSBOut ' if bus available, transmit data return End
Speed of USB EasyHID and Time problem
Originally Posted by sjohansson
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