The SAMD21 implementation is an adaption of @jimmo's code for STM32Lxx.
The only changes are the addresses and names of the port registers and the
timing parameters.
SAMD21: The precision is about +/-25ns at 48MHz clock frequency. The first
two cycles are about 40-60 ns longer than set. But still good enough to
drive a neopixel device.
SAMD51: The precision is about +/-30ns at 120MHz clock frequency. Good
enough to drive a neopixel device.
It suuports 1 channel @ 10 bit for SAMD21, 2 channels @ 12 bit for SAMD51.
Instantiation by:
dac = machine.DAC(ch) # 0 or 1
Method write:
dac.write(value)
The output voltage range is 0..Vdd.
All board pins that have UART's assigned can be used. Baud rate range is
75 Baud to ~2 MBaud.
No flow control yet, and only RX is buffered. TX buffer and flow control
may be added later for SAMD51 with its larger RAM and Flash.
Features are:
- 3 to 5 different frequency groups.
- Freq range of 1Hz - 24 MHz.
- Duty rate stays stable on freq change.
Keyword options to the PWM constructor:
- device=n Select a specific PWM device. If no device is specified, a free
device is chosen, if available at that pin.
- freq=nnnn
- duty_u16=nnnn
- duty_ns=nnnn
- invert=True/False Allowing two outputs on the same device/channel to have
complementary signals.
If both freq and duty are provided, PWM output will start immediately.
Pins at the same device have the same frequency. If the PWM output number
exceeds the number of channels at the PWM device, the effctive channel_no
is output_no % channel_count. So with a channel count of 4, output 7 is
assigned to channel 3. Pins at a certain channel have the same frequency
and duty rate, but may be seperately inverted.
With the method read_u16(). Keyword arguments of the constructor are:
- bits=n The resolution; default is 12.
- average=n The average of samples, which are taken and cumulated. The
default value is 16. Averaging by hw is faster than averaging
in code.
The ADC runs at a clock freq 1.5 MHz. A single 12 bit conversion takes
8 microseconds.
It's no longer needed because this macro is now processed after
preprocessing the source code via cpp (in the qstr extraction stage), which
means unused MP_REGISTER_MODULE's are filtered out by the preprocessor.
Signed-off-by: Damien George <damien@micropython.org>
