From e87156263cdf33d930efc5fc438208f99a557112 Mon Sep 17 00:00:00 2001
From: Cullen Jennings <fluffy@iii.ca>
Date: Sun, 22 May 2016 09:33:55 -0600
Subject: [PATCH] fix bug with negative currents and add Power

---
 samples/ina219.go       |  9 +++++++--
 sensor/ina219/ina219.go | 27 +++++++++++++++++++++++----
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/samples/ina219.go b/samples/ina219.go
index 43de691..c73d963 100644
--- a/samples/ina219.go
+++ b/samples/ina219.go
@@ -23,7 +23,7 @@ func main() {
 
 	bus := embd.NewI2CBus(1)
 
-	ina := ina219.New(bus, 0x40, 0.1)
+	ina := ina219.New(bus, 0x40, 0.001)
 	defer ina.Close()
 
 	for {
@@ -42,7 +42,12 @@ func main() {
 			panic(err)
 		}
 
-		fmt.Printf("Shunt Voltage=%v  Voltage=%v Current=%v\n", sv, v, c)
+		p, err := ina.Power()
+		if err != nil {
+			panic(err)
+		}
+
+		fmt.Printf("Shunt Voltage=%v  Voltage=%v Current=%v Power=%v \n", sv, v, c, p)
 
 		time.Sleep(500 * time.Millisecond)
 	}
diff --git a/sensor/ina219/ina219.go b/sensor/ina219/ina219.go
index 5cc76c3..795bdba 100644
--- a/sensor/ina219/ina219.go
+++ b/sensor/ina219/ina219.go
@@ -3,6 +3,7 @@
 // interfcace.
 
 // TODO - add options to config voltage range, sensitivity and averaging
+// TODO - add documentation
 
 package ina219
 
@@ -54,7 +55,10 @@ func (d *INA219) setup() error {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	config := uint16(0x219F) // 12, bit no integration, 32v bus range , 40mV shunt range
+	//config := uint16(0x219F) // 12, bit no integration, 32v bus range , 40mV shunt range
+	//config := uint16(0x2777) // 12, bit 64x integration, 32v bus range , 40mV shunt range
+	config := uint16(0x2F77) // 12, bit 64x integration, 32v bus range , 80mV shunt range
+	
 	err := d.Bus.WriteWordToReg(d.address, configReg, config)
 	if err != nil {
 		return err
@@ -62,7 +66,7 @@ func (d *INA219) setup() error {
 
 	calib := uint16(0.5 + 40.96/d.shuntResitance)
 
-	err = d.Bus.WriteWordToReg(d.address, calibReg, calib) // .1 ohm sense resitor
+	err = d.Bus.WriteWordToReg(d.address, calibReg, calib) 
 	if err != nil {
 		return err
 	}
@@ -84,7 +88,7 @@ func (d *INA219) ShuntVoltage() (float64, error) {
 		return math.NaN(), err
 	}
 
-	voltage := float64(v) / 100000.0
+	voltage := float64( int16(v) ) / 100000.0
 
 	return voltage, nil
 }
@@ -114,7 +118,22 @@ func (d *INA219) Current() (float64, error) {
 		return math.NaN(), err
 	}
 
-	current := float64(v) / 1000.0
+	current := float64( int16(v) ) / 1000.0
+
+	return current, nil
+}
+
+func (d *INA219) Power() (float64, error) {
+	if err := d.setup(); err != nil {
+		return math.NaN(), err
+	}
+
+	v, err := d.Bus.ReadWordFromReg(d.address, powerReg)
+	if err != nil {
+		return math.NaN(), err
+	}
+
+	current := float64( int16(v) ) / 50.0
 
 	return current, nil
 }