Msk Modem; Generic Framing - STMicroelectronics STM32WLEx Reference Manual

Sub-GHz radio (SUBGHZ)
index. An optional Gaussian filter can be used. All modulation parameters are set using
Set_ModulationParams() command.
The bit rate (or equivalent chip) is referenced to the HSE32 frequency and controlled by the
BR parameter, defined as follows:
BR = 32 x HSE32
FSK modulation is performed inside the RF-PLL bandwidth, by changing the fractional
divider. The high resolution of the RF-PLL allows very narrow frequency deviation. The
frequency deviation parameter Fdev, is one of the parameters in
Set_ModulationParams(). Fdev is defined as follows:
Fdev= Fdev[Hz] / FreqStep where FreqStep = HSE32
To ensure correct modulation, the following limit applies: (Fdev + BR/2) < BW.
The bandwidth must be chosen so that:
BW[DSB] > BR + 2 x frequency deviation + frequency error
where frequency error = 2 x HSE32
The FSK modem offers several pulse shape options in the PulseShape parameter.
4.5.4

MSK modem

The MSK modem provides a 2-MSK modulation over a range of data rates from 0.1 Kbit/s
up to 10 Kbit/s. This MSK modulation is only available in transmit mode. The modulation
index is automatically adjusted to 0.5. An optional Gaussian filter can be used. All
modulation parameters are set using Set_ModulationParams() command.
The bit rate (or equivalent chip) is referenced to the HSE32 frequency and controlled by the
BR parameter, defined as follows:
BR = HSE32
4.5.5

Generic framing

The generic packet framing is used with the FSK and MSK modems.
The generic packet provides a conventional packet format for applications in proprietary
NRZ coded, long range, low-energy communication links. The generic packet framing can
be configured by Set_PacketParams() command and allows whitening based on pseudo
random number generation, CRC operations and packet acknowledgment.
The following types of generic packet formats are available:
•
Variable length packet: including a short header (named length) that contains
information about the number of payload bytes
•
Fixed length packet: no header
In both packet formats, the payload length is limited to 254 when the address filtering is
activated.
120/1306
/ BitRate where HSE32
FREQ
FREQ
/ BitRate where HSE32
FREQ
RM0461 Rev 5
= 32 MHz
FREQ
FREQ
error
= 32 MHz
FREQ
RM0461
25
/ 2