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soypat
78 lines
2.3 KiB
Go
78 lines
2.3 KiB
Go
// Package mma8653 provides a driver for the MMA8653 3-axis accelerometer by
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// Freescale/NXP.
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//
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// Datasheet:
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// https://www.nxp.com/docs/en/data-sheet/MMA8653FC.pdf
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package mma8653 // import "tinygo.org/x/drivers/mma8653"
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import (
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"tinygo.org/x/drivers"
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"tinygo.org/x/drivers/internal/legacy"
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)
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// Device wraps an I2C connection to a MMA8653 device.
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type Device struct {
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bus drivers.I2C
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Address uint16
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sensitivity Sensitivity
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}
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// New creates a new MMA8653 connection. The I2C bus must already be
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// configured.
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//
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// This function only creates the Device object, it does not touch the device.
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func New(bus drivers.I2C) Device {
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return Device{bus, Address, Sensitivity2G}
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}
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// Connected returns whether a MMA8653 has been found.
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// It does a "who am I" request and checks the response.
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func (d Device) Connected() bool {
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data := []byte{0}
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legacy.ReadRegister(d.bus, uint8(d.Address), WHO_AM_I, data)
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return data[0] == 0x5A
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}
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// Configure sets up the device for communication.
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func (d *Device) Configure(speed DataRate, sensitivity Sensitivity) error {
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// Set mode to STANDBY to be able to change the sensitivity.
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err := legacy.WriteRegister(d.bus, uint8(d.Address), CTRL_REG1, []uint8{0})
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if err != nil {
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return err
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}
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// Set sensitivity (2G, 4G, 8G).
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err = legacy.WriteRegister(d.bus, uint8(d.Address), XYZ_DATA_CFG, []uint8{uint8(sensitivity)})
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if err != nil {
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return err
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}
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d.sensitivity = sensitivity
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// Set mode to ACTIVE and set the data rate.
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err = legacy.WriteRegister(d.bus, uint8(d.Address), CTRL_REG1, []uint8{(uint8(speed) << 3) | 1})
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if err != nil {
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return err
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}
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return nil
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}
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// ReadAcceleration reads the current acceleration from the device and returns
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// it in µg (micro-gravity). When one of the axes is pointing straight to Earth
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// and the sensor is not moving the returned value will be around 1000000 or
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// -1000000.
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func (d Device) ReadAcceleration() (x int32, y int32, z int32, err error) {
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data := make([]byte, 6)
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err = legacy.ReadRegister(d.bus, uint8(d.Address), OUT_X_MSB, data)
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shift := uint32(8)
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switch d.sensitivity {
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case Sensitivity4G:
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shift = 7
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case Sensitivity8G:
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shift = 6
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}
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x = int32(int16((uint16(data[0])<<8)|uint16(data[1]))) * 15625 >> shift
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y = int32(int16((uint16(data[2])<<8)|uint16(data[3]))) * 15625 >> shift
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z = int32(int16((uint16(data[4])<<8)|uint16(data[5]))) * 15625 >> shift
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return
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}
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