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ina219: Fix currentLSB calculation (#319)

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- currentLSB is supposed to be Maximum Expected Current / 2^15
  2 << 15 is 2^16, not 2^15.
- fix rounding error in powerLSB calculation
- check for overflow in calibration
- fix doc
pull/1/head
Nikola Kovacs 8 years ago committed by M-A
parent 15e8b246b2
commit 233d57b937
3 changed files with 34 additions and 31 deletions
Show Stats Download Patch File Download Diff File

2
experimental/devices/ina219/doc.go
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@ -8,7 +8,7 @@
// Calibration
//
// Calibration is recommended for accurate current and power measurements.
// Voltage measurements do not require sensor calibration. To calibrate meansure
// Voltage measurements do not require sensor calibration. To calibrate, measure
// the actual value of the shunt resistor.
//
// Datasheet

12
experimental/devices/ina219/ina219.go
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@ -157,13 +157,16 @@ func (d *Dev) calibrate(sense physic.ElectricResistance, maxCurrent physic.Elect
d.mu.Lock()
defer d.mu.Unlock()
d.currentLSB = maxCurrent / (2 << 15)
d.powerLSB = physic.Power(d.currentLSB * 20)
d.currentLSB = maxCurrent / (1 << 15)
d.powerLSB = physic.Power((maxCurrent*20 + (1 << 14)) / (1 << 15))
// Calibration Register = 0.04096 / (current LSB * Shunt Resistance)
// Where lsb is in Amps and resistance is in ohms.
// Calibration register is 16 bits.
cal := uint16(calibratescale / (int64(d.currentLSB) * int64(sense)))
return d.m.WriteUint16(calibrationRegister, cal)
cal := calibratescale / (int64(d.currentLSB) * int64(sense))
if cal >= (1 << 16) {
return errCalibrationOverflow
}
return d.m.WriteUint16(calibrationRegister, uint16(cal))
}
// PowerMonitor represents measurements from ina219 sensor.
@ -189,4 +192,5 @@ var (
errMaxCurrentInvalid = errors.New("max current cannot be negative or zero")
errRegisterOverflow = errors.New("bus voltage register overflow")
errWritingToConfigRegister = errors.New("failed to write to configuration register")
errCalibrationOverflow = errors.New("calibration would exceed maximum scaling")
)

51
experimental/devices/ina219/ina219_go1_7_test.go
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@ -36,12 +36,12 @@ func TestNew(t *testing.T) {
}{
{name: "defaults",
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
},
want: fields{
currentLSB: 48828 * physic.NanoAmpere,
powerLSB: 976560 * physic.NanoWatt,
currentLSB: 97656 * physic.NanoAmpere,
powerLSB: 1953125 * physic.NanoWatt,
},
},
{name: "badAddressOption",
@ -59,36 +59,36 @@ func TestNew(t *testing.T) {
{name: "setAddress",
opts: Opts{Address: 0x41},
tx: []i2ctest.IO{
{Addr: 0x41, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x41, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x41, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
},
want: fields{
currentLSB: 48828 * physic.NanoAmpere,
powerLSB: 976560 * physic.NanoWatt,
currentLSB: 97656 * physic.NanoAmpere,
powerLSB: 1953125 * physic.NanoWatt,
},
err: nil,
},
{name: "setMaxCurrent",
opts: Opts{MaxCurrent: 1000 * physic.MilliAmpere},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x68, 0xdc}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x34, 0x6e}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
},
want: fields{
currentLSB: 15258 * physic.NanoAmpere,
powerLSB: 305160 * physic.NanoWatt,
currentLSB: 30517 * physic.NanoAmpere,
powerLSB: 610352 * physic.NanoWatt,
},
err: nil,
},
{name: "setSenseResistor",
opts: Opts{SenseResistor: 10 * physic.MilliOhm},
opts: Opts{SenseResistor: 20 * physic.MilliOhm},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x47, 0xae}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x51, 0xeb}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
},
want: fields{
currentLSB: 48828 * physic.NanoAmpere,
powerLSB: 976560 * physic.NanoWatt,
currentLSB: 97656 * physic.NanoAmpere,
powerLSB: 1953125 * physic.NanoWatt,
},
err: nil,
},
@ -103,7 +103,7 @@ func TestNew(t *testing.T) {
},
{name: "errWritingToConfigRegister",
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister}, R: []byte{}},
},
want: fields{
@ -177,7 +177,7 @@ func TestSense(t *testing.T) {
err: errReadShunt,
args: Opts{},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
{Addr: 0x40, W: []byte{shuntVoltageRegister}, R: []byte{}},
},
@ -187,7 +187,7 @@ func TestSense(t *testing.T) {
err: errReadBus,
args: Opts{},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
{Addr: 0x40, W: []byte{shuntVoltageRegister}, R: []byte{0x00, 0x00}},
{Addr: 0x40, W: []byte{busVoltageRegister}, R: []byte{}},
@ -198,7 +198,7 @@ func TestSense(t *testing.T) {
err: errReadCurrent,
args: Opts{},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
{Addr: 0x40, W: []byte{shuntVoltageRegister}, R: []byte{0x00, 0x00}},
{Addr: 0x40, W: []byte{busVoltageRegister}, R: []byte{0x00, 0x00}},
@ -210,7 +210,7 @@ func TestSense(t *testing.T) {
err: errReadPower,
args: Opts{},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
{Addr: 0x40, W: []byte{shuntVoltageRegister}, R: []byte{0x00, 0x00}},
{Addr: 0x40, W: []byte{busVoltageRegister}, R: []byte{0x00, 0x00}},
@ -223,7 +223,7 @@ func TestSense(t *testing.T) {
err: nil,
args: Opts{},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
{Addr: 0x40, W: []byte{shuntVoltageRegister}, R: []byte{0x00, 0x00}},
{Addr: 0x40, W: []byte{busVoltageRegister}, R: []byte{0x00, 0x00}},
@ -237,7 +237,7 @@ func TestSense(t *testing.T) {
err: errRegisterOverflow,
args: Opts{},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{calibrationRegister, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{calibrationRegister, 0x10, 0x62}, R: []byte{}},
{Addr: 0x40, W: []byte{configRegister, 0x1f, 0xff}, R: []byte{}},
{Addr: 0x40, W: []byte{shuntVoltageRegister}, R: []byte{0x00, 0x00}},
{Addr: 0x40, W: []byte{busVoltageRegister}, R: []byte{0x00, 0x01}},
@ -315,13 +315,12 @@ func TestCalibrate(t *testing.T) {
err: errMaxCurrentInvalid,
},
{
name: "errIO",
name: "errCalibrationOverflow",
args: fields{
sense: physic.MilliOhm,
maxCurrent: physic.Ampere,
},
err: stringErr,
errString: "unexpected Tx",
err: errCalibrationOverflow,
},
{
name: "default",
@ -330,11 +329,11 @@ func TestCalibrate(t *testing.T) {
maxCurrent: 3200 * physic.MilliAmpere,
},
want: fields{
currentLSB: 48828 * physic.NanoAmpere,
powerLSB: 976560 * physic.NanoWatt,
currentLSB: 97656 * physic.NanoAmpere,
powerLSB: 1953125 * physic.NanoWatt,
},
tx: []i2ctest.IO{
{Addr: 0x40, W: []byte{0x05, 0x20, 0xc4}, R: []byte{}},
{Addr: 0x40, W: []byte{0x05, 0x10, 0x62}, R: []byte{}},
},
err: nil,
},

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