From c5dbe18be1213376fd7832d07c87ea3d455847d3 Mon Sep 17 00:00:00 2001
From: Lucas Bremgartner <lucas@bremis.ch>
Date: Fri, 28 Oct 2022 20:37:12 +0200
Subject: [PATCH] lsm303agr: fix I2C address auto increment for multi data read

fixes: #475
---
 lsm303agr/lsm303agr.go |  6 +++---
 lsm303agr/registers.go | 49 +++++++++++++++++++++++++-----------------
 2 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/lsm303agr/lsm303agr.go b/lsm303agr/lsm303agr.go
index 39bf84f..55cd9bd 100644
--- a/lsm303agr/lsm303agr.go
+++ b/lsm303agr/lsm303agr.go
@@ -137,7 +137,7 @@ func (d *Device) Configure(cfg Configuration) (err error) {
 // -1000000.
 func (d *Device) ReadAcceleration() (x, y, z int32, err error) {
 	data := d.buf[:6]
-	err = d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_X_L_A, data)
+	err = d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_AUTO_INC, data)
 	if err != nil {
 		return
 	}
@@ -190,7 +190,7 @@ func (d *Device) ReadMagneticField() (x, y, z int32, err error) {
 	}
 
 	data := d.buf[0:6]
-	d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_X_L_M, data)
+	d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_AUTO_INC, data)
 
 	x = int32(int16((uint16(data[1])<<8 | uint16(data[0]))))
 	y = int32(int16((uint16(data[3])<<8 | uint16(data[2]))))
@@ -219,7 +219,7 @@ func (d *Device) ReadCompass() (h int32, err error) {
 func (d *Device) ReadTemperature() (t int32, err error) {
 
 	data := d.buf[:2]
-	err = d.bus.ReadRegister(uint8(d.AccelAddress), OUT_TEMP_L_A, data)
+	err = d.bus.ReadRegister(uint8(d.AccelAddress), OUT_TEMP_AUTO_INC, data)
 	if err != nil {
 		return
 	}
diff --git a/lsm303agr/registers.go b/lsm303agr/registers.go
index 6767f2f..11e511c 100644
--- a/lsm303agr/registers.go
+++ b/lsm303agr/registers.go
@@ -6,31 +6,40 @@ const (
 	ACCEL_ADDRESS = 0x19
 	MAG_ADDRESS   = 0x1E
 
+	// i2C 8-bit subaddress (SUB): the 7 LSb represent the actual register address
+	// while the MSB enables address auto increment.
+	// If the MSb of the SUB field is 1, the SUB (register address) is
+	// automatically increased to allow multiple data read/writes.
+	ADDR_AUTO_INC_MASK = 0x80
+
 	// accelerometer registers.
-	ACCEL_WHO_AM_I    = 0x0F
-	ACCEL_CTRL_REG1_A = 0x20
-	ACCEL_CTRL_REG4_A = 0x23
-	ACCEL_OUT_X_L_A   = 0x28
-	ACCEL_OUT_X_H_A   = 0x29
-	ACCEL_OUT_Y_L_A   = 0x2A
-	ACCEL_OUT_Y_H_A   = 0x2B
-	ACCEL_OUT_Z_L_A   = 0x2C
-	ACCEL_OUT_Z_H_A   = 0x2D
+	ACCEL_WHO_AM_I     = 0x0F
+	ACCEL_CTRL_REG1_A  = 0x20
+	ACCEL_CTRL_REG4_A  = 0x23
+	ACCEL_OUT_X_L_A    = 0x28
+	ACCEL_OUT_X_H_A    = 0x29
+	ACCEL_OUT_Y_L_A    = 0x2A
+	ACCEL_OUT_Y_H_A    = 0x2B
+	ACCEL_OUT_Z_L_A    = 0x2C
+	ACCEL_OUT_Z_H_A    = 0x2D
+	ACCEL_OUT_AUTO_INC = ACCEL_OUT_X_L_A | ADDR_AUTO_INC_MASK
 
 	// magnetic sensor registers.
-	MAG_WHO_AM_I  = 0x4F
-	MAG_MR_REG_M  = 0x60
-	MAG_OUT_X_L_M = 0x68
-	MAG_OUT_X_H_M = 0x69
-	MAG_OUT_Y_L_M = 0x6A
-	MAG_OUT_Y_H_M = 0x6B
-	MAG_OUT_Z_L_M = 0x6C
-	MAG_OUT_Z_H_M = 0x6D
+	MAG_WHO_AM_I     = 0x4F
+	MAG_MR_REG_M     = 0x60
+	MAG_OUT_X_L_M    = 0x68
+	MAG_OUT_X_H_M    = 0x69
+	MAG_OUT_Y_L_M    = 0x6A
+	MAG_OUT_Y_H_M    = 0x6B
+	MAG_OUT_Z_L_M    = 0x6C
+	MAG_OUT_Z_H_M    = 0x6D
+	MAG_OUT_AUTO_INC = MAG_OUT_X_L_M | ADDR_AUTO_INC_MASK
 
 	// temperature sensor registers.
-	TEMP_CFG_REG_A = 0x1F
-	OUT_TEMP_L_A   = 0x0C
-	OUT_TEMP_H_A   = 0x0D
+	TEMP_CFG_REG_A    = 0x1F
+	OUT_TEMP_L_A      = 0x0C
+	OUT_TEMP_H_A      = 0x0D
+	OUT_TEMP_AUTO_INC = OUT_TEMP_L_A | ADDR_AUTO_INC_MASK
 
 	// accelerometer power mode.
 	ACCEL_POWER_NORMAL = 0x00 // default