From 6f0ace91575a3b2ae1b4d44c337ef8fdbf5bdbc8 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sun, 18 Nov 2018 20:24:04 +0100
Subject: [PATCH] mag3110: add driver

---
 mag3110/mag3110.go   | 55 ++++++++++++++++++++++++++++++++++++++++++++
 mag3110/registers.go | 28 ++++++++++++++++++++++
 2 files changed, 83 insertions(+)
 create mode 100644 mag3110/mag3110.go
 create mode 100644 mag3110/registers.go

diff --git a/mag3110/mag3110.go b/mag3110/mag3110.go
new file mode 100644
index 0000000..47133a9
--- /dev/null
+++ b/mag3110/mag3110.go
@@ -0,0 +1,55 @@
+// Package mag3110 implements a driver for the MAG3110 3-axis magnetometer by
+// Freescale/NXP.
+//
+// Datasheet: https://www.nxp.com/docs/en/data-sheet/MAG3110.pdf
+package mag3110
+
+import (
+	"machine"
+)
+
+// Device wraps an I2C connection to a MAG3110 device.
+type Device struct {
+	bus machine.I2C
+}
+
+// NewI2C creates a new MAG3110 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 MAG3110 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] == 0xC4
+}
+
+// Configure sets up the device for communication.
+func (d Device) Configure() {
+	d.bus.WriteRegister(Address, CTRL_REG2, []uint8{0x80}) // Power down when not used
+}
+
+// ReadMagnetic reads the vectors of the magnetic field of the device and
+// returns it.
+func (d Device) ReadMagnetic() (x int16, y int16, z int16) {
+	d.bus.WriteRegister(Address, CTRL_REG1, []uint8{0x1a}) // Request a measurement
+
+	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
+}
+
+// ReadTemperature reads the current die temperature in degrees Celsius.
+func (d Device) ReadTemperature() (temp int8) {
+	data := make([]byte, 1)
+	d.bus.ReadRegister(Address, DIE_TEMP, data)
+	return int8(data[0])
+}
diff --git a/mag3110/registers.go b/mag3110/registers.go
new file mode 100644
index 0000000..a2f0347
--- /dev/null
+++ b/mag3110/registers.go
@@ -0,0 +1,28 @@
+package mag3110
+
+// Constants/addresses used for I2C.
+
+// The I2C address which this device listens to.
+const Address = 0x0E
+
+// Registers. Names, addresses and comments are copied from the datasheet.
+const (
+	DR_STATUS = 0x00 // Data ready status per axis
+	OUT_X_MSB = 0x01 // Bits [15:8] of X measurement
+	OUT_X_LSB = 0x02 // Bits [7:0] of X measurement
+	OUT_Y_MSB = 0x03 // Bits [15:8] of Y measurement
+	OUT_Y_LSB = 0x04 // Bits [7:0] of Y measurement
+	OUT_Z_MSB = 0x05 // Bits [15:8] of Z measurement
+	OUT_Z_LSB = 0x06 // Bits [7:0] of Z measurement
+	WHO_AM_I  = 0x07 // Device ID Number
+	SYSMOD    = 0x08 // Current System Mode
+	OFF_X_MSB = 0x09 // Bits [14:7] of user X offset
+	OFF_X_LSB = 0x0A // Bits [6:0] of user X offset
+	OFF_Y_MSB = 0x0B // Bits [14:7] of user Y offset
+	OFF_Y_LSB = 0x0C // Bits [6:0] of user Y offset
+	OFF_Z_MSB = 0x0D // Bits [14:7] of user Z offset
+	OFF_Z_LSB = 0x0E // Bits [6:0] of user Z offset
+	DIE_TEMP  = 0x0F // Temperature, signed 8 bits in °C
+	CTRL_REG1 = 0x10 // Operation modes
+	CTRL_REG2 = 0x11 // Operation modes
+)