While trying different my NET nanoFramework Semtech SX127X library configurations so I could explore the interactions of RegOcp(Over current protection) + RegOcpTrim I noticed something odd about the power consumption so I revisited how the output power is calculated.
The RegPaConfig register has three settings PaSelect(RFO & PA_BOOST), MaxPower(0..7), and OutputPower(0..15). When in RFO mode the pOut has a range of -4 to 15 and PA_BOOST mode has a range of 2 to 20.
The SX127X also has a power amplifier attached to the PA_BOOST pin and a higher power amplifier which is controlled by the RegPaDac register.
// Set RegPAConfig & RegPaDac if powerAmplifier/OutputPower settings not defaults
if ((powerAmplifier != Configuration.RegPAConfigPASelect.Default) || (outputPower != Configuration.OutputPowerDefault))
{
if (powerAmplifier == Configuration.RegPAConfigPASelect.PABoost)
{
byte regPAConfigValue = (byte)Configuration.RegPAConfigPASelect.PABoost;
// Validate the minimum and maximum PABoost outputpower
if ((outputPower < Configuration.OutputPowerPABoostMin) || (outputPower > Configuration.OutputPowerPABoostMax))
{
throw new ApplicationException($"PABoost {outputPower}dBm Min power {Configuration.OutputPowerPABoostMin} to Max power {Configuration.OutputPowerPABoostMax}");
}
if (outputPower <= Configuration.OutputPowerPABoostPaDacThreshhold)
{
// outputPower 0..15 so pOut is 2=17-(15-0)...17=17-(15-15)
regPAConfigValue |= (byte)Configuration.RegPAConfigMaxPower.Default;
regPAConfigValue |= (byte)(outputPower - 2);
_registerManager.WriteByte((byte)Configuration.Registers.RegPAConfig, regPAConfigValue);
_registerManager.WriteByte((byte)Configuration.Registers.RegPaDac, (byte)Configuration.RegPaDac.Normal);
}
else
{
// outputPower 0..15 so pOut is 5=20-(15-0)...20=20-(15-15) // See https://github.com/adafruit/RadioHead/blob/master/RH_RF95.cpp around line 411 could be 23dBm
regPAConfigValue |= (byte)Configuration.RegPAConfigMaxPower.Default;
regPAConfigValue |= (byte)(outputPower - 5);
_registerManager.WriteByte((byte)Configuration.Registers.RegPAConfig, regPAConfigValue);
_registerManager.WriteByte((byte)Configuration.Registers.RegPaDac, (byte)Configuration.RegPaDac.Boost);
}
}
else
{
byte regPAConfigValue = (byte)Configuration.RegPAConfigPASelect.Rfo;
// Validate the minimum and maximum RFO outputPower
if ((outputPower < Configuration.OutputPowerRfoMin) || (outputPower > Configuration.OutputPowerRfoMax))
{
throw new ApplicationException($"RFO {outputPower}dBm Min power {Configuration.OutputPowerRfoMin} to Max power {Configuration.OutputPowerRfoMax}");
}
// Set MaxPower and Power calculate pOut = PMax-(15-outputPower), pMax=10.8 + 0.6*MaxPower
if (outputPower > Configuration.OutputPowerRfoThreshhold)
{
// pMax 15=10.8+0.6*7 with outputPower 0...15 so pOut is 15=pMax-(15-0)...0=pMax-(15-15)
regPAConfigValue |= (byte)Configuration.RegPAConfigMaxPower.Max;
regPAConfigValue |= (byte)(outputPower + 0);
}
else
{
// pMax 10.8=10.8+0.6*0 with output power 0..15 so pOut is -4=10-(15-0)...10.8=10.8-(15-15)
regPAConfigValue |= (byte)Configuration.RegPAConfigMaxPower.Min;
regPAConfigValue |= (byte)(outputPower + 4);
}
_registerManager.WriteByte((byte)Configuration.Registers.RegPAConfig, regPAConfigValue);
_registerManager.WriteByte((byte)Configuration.Registers.RegPaDac, (byte)Configuration.RegPaDac.Normal);
}
}
// Set RegOcp if any of the settings not defaults
if ((ocpOn != Configuration.RegOcp.Default) || (ocpTrim != Configuration.RegOcpTrim.Default))
{
byte regOcpValue = (byte)ocpTrim;
regOcpValue |= (byte)ocpOn;
_registerManager.WriteByte((byte)Configuration.Registers.RegOcp, regOcpValue);
}
After reviewing the code I realised that the the RegPaDac test around line 14 should <= rather than <
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