mma8653: add driver

mma8653/mma8653.go

@@ -0,0 +1,47 @@
+// Package mma8653 provides a driver for the MMA8653 3-axis accelerometer by
+// Freescale/NXP.
+//
+// Datasheet:
+// https://www.nxp.com/docs/en/data-sheet/MMA8653FC.pdf
+package mma8653
+
+import (
+	"machine"
+)
+
+// Device wraps an I2C connection to a MMA8653 device.
+type Device struct {
+	bus machine.I2C
+}
+
+// NewI2C creates a new MMA8653 connection. The I2C bus must already be
+// configured.
+//
+// This function only creates the Device object, it does not touch the device.
+func NewI2C(bus machine.I2C) Device {
+	return Device{bus}
+}
+
+// Connected returns whether a MMC8653 has been found.
+// It does a "who am I" request and checks the response.
+func (d Device) Connected() bool {
+	data := []byte{0}
+	d.bus.ReadRegister(Address, WHO_AM_I, data)
+	return data[0] == 0x5A
+}
+
+// Configure sets up the device for communication.
+func (d Device) Configure(speed DataRate) {
+	data := (uint8(speed) << 3) | 1 // set data rate and ACTIVE mode
+	d.bus.WriteRegister(Address, CTRL_REG1, []uint8{data})
+}
+
+// ReadOrientation reads the current orientation from the device and returns it.
+func (d Device) ReadOrientation() (x int16, y int16, z int16) {
+	data := make([]byte, 6)
+	d.bus.ReadRegister(Address, OUT_X_MSB, data)
+	x = int16((uint16(data[0]) << 8) | uint16(data[1]))
+	y = int16((uint16(data[2]) << 8) | uint16(data[3]))
+	z = int16((uint16(data[4]) << 8) | uint16(data[5]))
+	return
+}

mma8653/registers.go

@@ -0,0 +1,53 @@
+package mma8653
+
+// Constants/addresses used for I2C.
+
+// The I2C address which this device listens to.
+const Address = 0x1D
+
+// Registers. Names, addresses and comment copied from the datasheet.
+const (
+	STATUS       = 0x00 // Real time status
+	OUT_X_MSB    = 0x01 // top 8 bits of 10-bit sample
+	OUT_X_LSB    = 0x02 // bottom 2 bits of 10-bit sample
+	OUT_Y_MSB    = 0x03 // top 8 bits of 10-bit sample
+	OUT_Y_LSB    = 0x04 // bottom 2 bits of 10-bit sample
+	OUT_Z_MSB    = 0x05 // top 8 bits of 10-bit sample
+	OUT_Z_LSB    = 0x06 // bottom 2 bits of 10-bit sample
+	SYSMOD       = 0x0B // Current System Mode
+	INT_SOURCE   = 0x0C // Interrupt status
+	WHO_AM_I     = 0x0D // Device ID (0x5A)
+	XYZ_DATA_CFG = 0x0E // Dynamic Range Settings
+	PL_STATUS    = 0x10 // Landscape/Portrait orientation status
+	PL_CFG       = 0x11 // Landscape/Portrait configuration
+	PL_COUNT     = 0x12 // Landscape/Portrait debouncer counter
+	PL_BF_ZCOMP  = 0x13 // Back/Front, Z-Lock Trip threshold
+	PL_THS_REG   = 0x14 // Portrait to Landscape Trip angle
+	FF_MT_CFG    = 0x15 // Freefall/Motion functional block configuration
+	FF_MT_SRC    = 0x16 // Freefall/Motion event source register
+	FF_MT_THS    = 0x17 // Freefall/Motion threshold register
+	FF_MT_COUNT  = 0x18 // Freefall/Motion debounce counter
+	ASLP_COUNT   = 0x29 // Counter setting for Auto-SLEEP/WAKE
+	CTRL_REG1    = 0x2A // Data Rates, ACTIVE Mode
+	CTRL_REG2    = 0x2B // Sleep Enable, OS Modes, RST, ST
+	CTRL_REG3    = 0x2C // Wake from Sleep, IPOL, PP_OD
+	CTRL_REG4    = 0x2D // Interrupt enable register
+	CTRL_REG5    = 0x2E // Interrupt pin (INT1/INT2) map
+	OFF_X        = 0x2F // X-axis offset adjust
+	OFF_Y        = 0x30 // Y-axis offset adjust
+	OFF_Z        = 0x31 // Z-axis offset adjust
+)
+
+type DataRate uint8
+
+// Data rate constants.
+const (
+	DataRate800Hz DataRate = iota // 800Hz,  1.25ms interval
+	DataRate400Hz                 // 400Hz,  2.5ms  interval
+	DataRate200Hz                 // 200Hz,  5ms    interval
+	DataRate100Hz                 // 100Hz,  10ms   interval
+	DataRate50Hz                  // 50Hz,   20ms   interval
+	DataRate12Hz                  // 12.5Hz, 80ms   interval
+	DataRate6Hz                   // 6.25Hz, 160ms  interval
+	DataRate2Hz                   // 1.56Hz, 640ms  interval
+)