How to configure S2-LP with SigFox stack for 16dBm output

[Central SUPPORT]

How can we increase the output power to 16dBm of S2-LP - in combination with the SigFox stack? In the SigFox_PushButton_Project we tried to set register PA_POWER8 to 0x01 to turn the output power up.

StatusByte = SdkEvalSpiWriteRegisters(0x5A, 0x01, pcBuffer);

Is this the right way how to do it?          

NOTE: This question and answer originated from a customer support case which was handled by us. We regularly review support cases and add any helpful ones here for all to benefit from.

[Central SUPPORT · Accepted solution]

Please note that S2-LP has been certified @ 14dBm for SigFox and not at 16dBm.

If you need 16dBm output power, you have to modify:

1.     SMPS voltage (bits SET_SMPS_LEVEL to be set at 0x7 in register PA_CONF0 0x42)

2.     PA_MAXDBM (bit 6 to be set to 0 in register PA_POWER0 0x62)

For this purpose, it is not possible to directly set the registers on application side (as it will be over-written by the SIGFOX RF library). The right way is to use the ST_RF_API_smps API, as follows, before opening the SIGFOX stack (SIGFOX_API_open):

ST_RF_API_smps(7);     

Please note that this will set the maximum output power, using Vsmps = 1.8V. But, the exact 16dBm is not guaranteed (discrepancy between devices output power can be observed).    

Such modification must be approved by SIGFOX, as the device output power is checked during P1 certification (in conducted mode).

[rastik]

Hello, which of the other registers influence the output power? In some situations I'd like to decrease the output power to save energy. Sigfox code is manipulating with the output buffer when reduced power is requested and not with PA_POWER settings.

And a bunch of related questions. Thank you in advance for answering them.

• What is the relation between SMPS voltage and output power?
• What should be the value for PA_POWER? Sigfox code is using PA_POWER8 with default value 0x01, unless ramping is used.
  • Is 0x01 the highest possible output power?
  • Is 0x00 the lowest power? And then the next is 0x7f? Or why is 0x00 the default for PA_POWER1?
  • What is the unit of PA_POWER?
• What does PA_MAXDBM do? You've stated to have it 0 for 16dBm, but the datasheet states it will use maximum power when set to 1.
• Sigfox code writes 1 to bit 1 of PM_CONF0. Datasheet states it's RESERVED. What is the meaning of this bit?
• Sigfox code writes 0x88 to PA_CONFIG0, if SMPS voltage higher than 1.5V is used. Again, these bit are RESERVED. What is the meaning of this setting?

[Thomas LB]

Hello,

I've been trying with no success yet to modify the output power through PA_POWER8 and PA_POWER0 config with no success.

The datasheet is not clear about this. Some 0.5db step is mentioned for power between -10dbm and +10dbm, somewhere else between -30dbm and +14dbm...

"Output power level" appear to be coded on 7bits but still lot of mysteri :(

Please Help ST, this product is great, don't mess the software part :p

Thanks

[jeffm]

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@Central SUPPORT wrote:

2.     PA_MAXDBM (bit 6 to be set to 0 in register PA_POWER0 0x62)

Is that correct? The datasheet says "set to 1: configure the PA to send maximum output power."