Field Programable Gate Array.
is a programmable chip.
Best Regards
Kim Mortensen
2008/9/22 Eric H. Johnson <[EMAIL PROTECTED]>
> Sebastian,
>
> I am not sure what you mean by the FPGA register. Do you mean the interface
> register between the driver and the m5i20, or the register actually
> handling
> the PWM within the FPGA? As I said in an earlier email (off list), I concur
> that the value being sent to the FPGA through the interface register is
> correct (providing the bit shift to bits 16-27 is where the value is
> supposed to go), which would confirm that my pwmgen.scale is set to 1.0.
>
> I was able to measure the duty cycle on a pain old multi-meter. At values
> of
> 0.125 and below, the voltage would start dropping from the almost 100% duty
> cycle voltage of just under 3.3V, and very linearly for the range of 0.125
> down to 0.0. The voltage reading from my meter was in fact very accurate.
>
> Here are the voltage readings I got:
>
> Value Voltage
> >=0.126 3.278
> 0.125 3.272
> 0.120 3.144
> 0.110 2.884
> 0.100 2.623
> 0.090 2.362
> 0.080 2.102
> 0.070 1.841
> 0.060 1.580
> 0.050 1.320
> 0.040 1.059
> 0.030 0.798
> 0.020 0.538
> 0.010 0.278
>
> Regards,
> Eric
>
>
> How are you measuring duty cycle?
>
> I'm confident that (at least in my test setup) setting pwmgen.XX.value
> causes the correct number to be set in the FPGA register.
>
> Take a look at <http://pastebin.ca/1208030>. I updated pwmgen.c to decode
> the number in the PWM Value Register, then used raw.dump-state to show the
> register when pwmgen.value was -1.0 to +0.3 in increments of 0.1. Lines
> 1-22 show the relevant dmesg output for .value=0, then I just show the PWM
> Value Register for the other .value settings.
>
> In addition to the correct numbers being set in the register, the
> corresponding LED on the 7i31 LED Debug board varies in intensity as
> expected, and the small DC servo (driven by a 7i30 servo amp) changes its
> speed as expected.
>
> I'm not sure why you're seeing what you're seeing. Is maybe your
> pwmgen.scale not set to 1.0?
>
>
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