2.1 KiB
sigma delta Module
This module provides access to the sigma-delta component. It's a hardware signal generator that can be routed to any of the GPIOs except pin 0.
The signal generation is controlled by the setprescale() and settarget() functions.
- 0 < target <= 128
thigh = (prescale + 1) / 80 µs
tperiod = thigh * 256 / target - 128 < target < 256
tlow = (prescale + 1) / 80 µs
tperiod = tlow * 256 / (256 - target) - target = 0
signal stopped at low
Fixed frequency PWM at ~312.5 kHz is availble with the setpwmduty() function.
sigma_delta.close()
Stops signal generation and reenables GPIO functionality at the specified pin.
Syntax
sigma_delta.close(pin)
Parameters
pin 1~12, IO index
Returns
nil
sigma_delta.setprescale()
Sets the prescale value.
Syntax
`sigma_delta.setprescale(value)
Parameters
value prescale 1 to 255
Returns
nil
See also
sigma_delta.setpwmduty()
Operate the sigma-delta module in PWM-like mode with fixed base frequency.
Syntax
sigma_delta.setpwmduty(ratio)
Parameters
ratio 0...255 for duty cycle 0...100%, 0 stops the signal at low
Returns
nil
Example
-- attach generator to pin 2
sigma_delta.setup(2)
-- set 50% duty cycle ratio (and implicitly start signal)
sigma_delta.setpwmduty(128)
-- stop
sigma_delta.setpwmduty(0)
-- resume with ~99.6% ratio
sigma_delta.setpwmduty(255)
-- stop and detach generator from pin 2
sigma_delta.close(2)
sigma_delta.settarget()
Sets the target value.
Syntax
`sigma_delta.settarget(value)
Parameters
value target 0 to 255
Returns
nil
See also
sigma_delta.setup()
Stops the signal generator and routes it to the specified pin.
Syntax
sigma_delta.setup(pin)
Parameters
pin 1~12, IO index
Returns
nil