MPL115A1 (a miniature SPI digital barometer, 50 to 115 kPa) operation sample for MicroPython

MPL115A1S.py

from	machine		import	SPI, Pin
from	utime		import	sleep, localtime
from	struct		import	unpack
import	os

class MPL115A1:
	def __init__( self, spi, cs ):
		self.spi	= spi
		self.cs		= cs
		self._get_coeff()
		
	def pressure( self ):
		self._cs_ctrl( 0 )
		self.spi.write( bytearray( [ 0x24, 0x00 ] ) )	
		self._cs_ctrl( 1 )

		sleep( 0.003 )

		p_adc, t_adc	= self._pressure_temp()
		
		p_comp	= self.a0 + (self.b1 + self.c12 * t_adc) * p_adc + self.b2 * t_adc
	 
		return p_comp * ((115 - 50) / 1023) + 50

	def _get_coeff( self ):
		data	= self._insert_zero_bytes( [ 0x88, 0x8A, 0x8C, 0x8E, 0x90, 0x92, 0x94, 0x96 ] )

		self._cs_ctrl( 0 )
		self.spi.write_readinto( data, data )
		self._cs_ctrl( 1 )
		
		self.a0, self.b1, self.b2, self.c12	= unpack( ">hhhh", self._collect_odd_bytes( data ) )
		
		self.a0		/= 2**3
		self.b1		/= 2**13
		self.b2		/= 2**14
		self.c12	/= 2**24

	def _pressure_temp( self ):
		data	= self._insert_zero_bytes( [ 0x80, 0x82, 0x84, 0x86  ] )
		
		self._cs_ctrl( 0 )
		self.spi.write_readinto( data, data )
		self._cs_ctrl( 1 )

		p, t	= unpack( ">HH", self._collect_odd_bytes( data ) )
		p	>>= 6
		t	>>= 6
		
		return ( p, t )

	def _collect_odd_bytes( self, data ):
		#	doing similar to data = data[1::2] because MicroPython doesn't support "::2"
		return bytearray( [ x for i, x in enumerate( data ) if i % 2 ] )

	def _insert_zero_bytes( self, data ):
		return bytearray( sum( [ [x, 0x00] for x in data ], [] ) + [ 0x00 ] )

	def _cs_ctrl( self, state ):
		if self.cs:
			self.cs.value( state )


def main():
	DEPTH		= 1000
	LOG_FILE	= "data.csv"
	SPI_FREQ	= 1000000

	if "MIMXRT" in os.uname().machine:
		spi		= SPI( 0, SPI_FREQ, cs = 0 )
		sensor	= MPL115A1( spi, None )
		led		= None
		
	elif "Raspberry Pi Pico" in os.uname().machine:
		spi		= SPI( 1, SPI_FREQ, sck = Pin( 10 ), mosi = Pin( 11 ), miso = Pin( 12 ) )
		sensor	= MPL115A1( spi, Pin( 13, Pin.OUT ) )
		led		= Pin( "LED", Pin.OUT )

	while True:
		p	= 0;
		
		for i in range( DEPTH ):
			p	+= sensor.pressure()
	
			if led:
				led.value( i >> 4 & 0x1 )

		dt	= localtime()
		p_str	= "{:04d}-{:02d}-{:02d} {:02d}:{:02d}:{:02d}, {}".format( dt[ 0 ], dt[ 1 ], dt[ 2 ], dt[ 3 ], dt[ 4 ], dt[ 5 ], p / DEPTH * 10 )
		print( p_str )

		with open( "data.csv", "a" ) as f:
			print( p_str, file = f )

if __name__ == "__main__":
	main()