piclist 2008\07\08\203003a >
Thread: Absolute -> Relocatable
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Notes for HV_PWM_proto project. It's incomplete as a whole
but the core generator is reasonably finished (well, it's working),
and PWM is being generated. It's proof-of-concept only at this
stage, some functions are not running yet

Variable duty cycle and variable frequency 6-bit PWM that retains
set duty cycle as frequency is varied within a 100Hz - 279Hz range

Basis is a count of 64 TMR0 interrupts

Duty Cycle pot sets the number of consecutive interrupts that are
a '1' on the output pin

Frequency pot changes the reload value of TMR0

On the 64th IRQ, duty cycle is updated

At other values of the IRQ counter, other ADC channels are (will
be) read and the LCD is updated from a print buffer

As the LCD's Busy Flag is not being used, two interrupt periods
separate any data write to the LCD. Writes should complete in
40us, and minimum IRQ period is 56us. Outside of the IRQ system,
LCD processing delays are used

Two "mysterious characters" appear at positions 0 and 1 as soon
as the LCD is updated for the first time under interrupt. Yet to
figure out where they're coming from. They aren't ASCII, look like
random data, maybe their origin will become clear when redefined
characters are used. Over-writing gets rid of them for now

Schematic - voltage limited to 28V for now. Battery maintenance,
regulators, efficiency, 4017 drive etc will be re-visited

<00c701c8e15a$933242b0$89aafea9@ivp1> 7bit

See also: www.piclist.com/techref/microchip/devices.htm?key=pic
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Subject (change) Absolute -> Relocatable

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