Prototype Alamatic Driver for BMP183

README.rst

Prototype Alamatic Driver for BMP183

This is just an exploration of what a real-world (if incomplete) BMP183 driver might look like with the current iteration of Alamatic's featureset.

It makes extensive use of the worker concept, which effectively creates a protothread that processes a queue of requests one at a time. A worker can await a promise, just like a Task can, but unlike a normal function.

This example seems to demonstrate that even this relatively simple example leads to a proliferation of workers, suggesting that if this concept is to work the protothreads must be very lightweight or else the program's memory and CPU usage could easily become dwarfed by protothread bookkeeping.

bmp183.alm

enum Register as UInt8:
    CONTROL = 0xf4
    TEMP_DATA = 0xf6

enum ControlCommand as UInt8:
    READ_TEMP = 0x2e
    READ_PRESSURE = 2x34

class BMP183(spi_channel, delay):

    worker begin(mode):
        spi_channel.begin()
        spi_channel.set_data_mode(MODE0)

        await spi_channel.write("hello world")

    worker _read_uint8_reg(reg as Register):
        await spi_channel.write([0x80 | reg.value])
        buf = Buffer(UInt8, 1)
        await spi_channel.read(buf)
        return buf[0]

    worker _read_uint16_reg(reg as Register):
        await spi_channel.write([0x80 | reg.value])
        buf = Buffer(UInt8, 2)
        await spi_channel.read(buf)
        return buf[0] << 8 | buf[1]

    worker _write_uint8_reg(reg as Register, value as UInt8):
        await spi_channel.write([0x7f & reg.value, value])

    func _write_control(cmd as ControlCommand):
        return _write_uint8_reg(CONTROL, cmd.value)

    worker get_temperature():
        ...

    func get_pressure():
        ...

    worker get_altitude(sea_level_pressure=101325):
        pressure = await get_pressure();
        # FIXME: This needs a conversion to float somewhere.
        altitude = 44330 * (1 - (pressure / sea_level_pressure) ** 0.1903)

    worker get_raw_temperature():
        await spi_channel.select()
        _write_control(READ_TEMP)
        await delay.ms(5)
        await _read_uint16_reg(TEMP_DATA)
        await spi_channel.deselect()

    func get_raw_pressure():
        pass

example.ala

import device/bmp183
import lpc1114
import format_writer

var spi_channel = lpc1114.spi_bus.create_channel(lpc1114.D1)
var sensor = bmp183.BMP183(spi_channel)
var format_writer = format_writer.FormatWriter(lpc1114.UART0)

loop:
    var temp = await sensor.get_temperature()
    var altitude = await sensor.get_altitude()

    await lpc1114.format_writer.write("Temperature: ", temp, "\n")
    await lpc1114.format_writer.write("Altitude: ", altitude, "\n")