STM32WLE5JC FHSS w/ LoRA Support

[JCB_STM]

Good afternoon,

I am currently investigating the FHSS in the STM32WLE5JC chip. Using the STM32 SubGHz radio stack

version 1.3.1 I am unable to use any of the settings with LoRa. Enabling the FHSS and setting

the period does not change anything and the messages are transmitted as if this was omitted.

It is my understanding that the radio IP is from Semtech, I cannot find much detail on if the

hardware is based exactly on a Semtech board (i.e, SX1262) or a custom implementation.

Back to LoRa FHSS have looked through the other forums and in 2020 an ST Employee said

it was not possible with the current stack, and in 2025 that it could be done

(but the example provided was for LR-FHSS which uses a different modulation scheme GMSK).

My questions:
Is the STM32WLE5JC hardware comparable to a specific Semtech chip (so I can understand the

limitations)?

Are the FHSS settings in the STM32 radio driver enabled for LoRa (it describes

the settings are LoRa specific)?

Thank You!

void ( *SetTxConfig )( RadioModems_t modem, int8_t power, uint32_t fdev,

uint32_t bandwidth, uint32_t datarate,

uint8_t coderate, uint16_t preambleLen,

 bool fixLen, bool crcOn, bool freqHopOn,

uint8_t hopPeriod, bool iqInverted, uint32_t timeout );

[JCB_STM]

links to discussions 

https://community.st.com/t5/stm32-mcus-wireless/lora-fhss-support-for-stm32wl55jc-e5-module/m-p/766777#M23140
https://community.st.com/t5/stm32-mcus-wireless/stm32wle5jc-about-frequency-hopping-at-915-mhz/td-p/264359?utm

[JCB_STM · Accepted solution]

After looking further it looks like the Semtech SX1262 chip does not support LoRa FHSS, this seems to be a hardware and not a driver limitation. There is no reference to LoRa FHSS in the driver code or documentation as well.

Contrary, the Semtech SX1276 chip does support LoRa FHSS. It has configurable settings directly in the driver with documented support.

The STM32WLE5JC does not appear to capable of LoRA FHSS from a hardware point of view as it is driven by the SX1262 chip. Why the Sub GHz stack includes this settings is still unknown, it has specific reference to LoRa. My assumption is they were confusing it with LR-FHSS which uses GMSK and is supported (why they chose to name it Long Range FHSS when LoRa FHSS exists is besides me).