cancel
Showing results for 
Search instead for 
Did you mean: 

NUCLEO-WL55JC1 Packet Loss

altoleoi
Associate

Hello,

my setup consists of 2 NUCLEO-WL55JC1 boards and an adapted version of the example project SubGHz_Phy_Per with which I can recognize the number of bit errors, RSSI of the latest received packet and some interrupts (IRQ_RX_DONE, IRQ_PREAMBLE_DETECTED, ..) using Serial Wire Viewer and STMViewer.

Modulation is 2GFSK.

Tx-Node sends every 10 ms a packet with 80 bytes.

Overview of modulation and packet parameters:

  • RF_FREQUENCY: 868000000 /* Hz */
  • TX_OUTPUT_POWER: 14 /* dBm */
  • FSK_FDEV: 74680 /* Hz */
  • FSK_DATARATE: 149360 /* bps */
  • FSK_BANDWIDTH: 300000 /* Hz */
  • FSK_PREAMBLE_LENGTH: 12 /* Byte, Same for Tx and Rx */
  • FSK_FIX_LENGTH_PAYLOAD_ON: true
  • PAYLOAD_LEN: 80 /* Byte */
  • ModulationShaping: RADIO_FSK_MOD_SHAPING_G_BT_1
  • PreambleMinDetect: RADIO_FSK_PREAMBLE_DETECTOR_08_BITS
  • whiteSeed: 0x01FF; /*WhiteningSeed*/
  • SyncWord: { 0xC1, 0x94, 0xC1}
  • CrcLength: RADIO_FSK_CRC_2_BYTES_IBM
  • CrcPolynomial: 0x8005
  • CrcSeed: 0xFFFF
  • Whitening: RADIO_FSK_DC_FREEWHITENING
  • StopTimerOnPreambleDetect: 0
  • AddrComp: RADIO_FSK_ADDRESSCOMP_FILT_OFF

My calculations of Rx BW and Tx Fdev refer to Semtech SX1261/2  RF Transceiver Datasheet (p.43, LoRa Connect Transceiver, SX1261, +15dBm for Global Coverage | Semtech).

(2*Fdev + BR) < BW

I am aware that the bit error rate depends on the SNR. I don't understand why numerous packet losses occur, even over short distances (indoor) and acceptable RSSI, screenshot from STMviewer:

Nucleo-WL55jC1_PacketLoss.png

Packet Loss increases for much too small or large BW, which is understandable.

 

What possible mistakes have I made?

If you need further information, I can of course add it.

 
2 REPLIES 2
STTwo-32
ST Employee

Hello @altoleoi 

The packet losses depend on a few characteristics (modulation, TX_OUTPUT_POWER...). Also, it can depend on different external characteristics such as the electromagnetic interference, the Antenna gain, ...

I suggest you try to use a direct line of sight (LOS) between both boards and increase the TX_OUTPUT_POWER to the max value.

Best Regards.

STTwo-32

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Hello @STTwo-32,

thank you for your reply.

The board is delivered with an omnidirectional compressed whip / stubby antenna with a gain of 2dBi (should be ANT-SS900), which "[...] is stuck to the SMA connector because of FCC constraints". "[...] the FCC implies that the antenna must be stuck to the board connector with epoxy glue" (UM2592 - Rev 2, p. 27), therefore there is no possibility to change the antenna to increase the receiver gain.

Due to regional regulations, the ERP is limited to a maximum of 14dBm (13.98dBm).

Unfortunately, the required application does not guarantee LOS.

 

Best Regards

altoleoi