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TMS320F28379D: LoRa Porting to TI Microcontroller

Davide Frasson
Prodigy 10 points
Part Number: TMS320F28379D

Hi at all,

I was trying to do the porting of the LoRa library of Arduino to implement this particular sensor that i link below (based on the SX1276 transceiver) : 

https://www.olimex.com/Products/IoT/LoRa/LoRa868/open-source-hardware

on my board. Everthing was actually fine, made the porting of the code reading the datasheet of the module, understood how the SPI connection between board and devices worked.

When i runned the code for debug purpose, i was able to read the register of the LoRa module in the way that i meant, actually reading the values that i expected, but when i tried to send real data via the antenna it didn't worked. I've analysed the output on the oscylloscope of the MISO and MOSI of the TI and it's pretty fine as the code says, but comparing the output from Arduino board was actually different. TI SPI is made by square waves, instead Arduino has waves more like sinusoides. Is it because of the SPI module of the TI that is better or what? I cannot understand why the LoRa communication is not working.

  • 0
    TI__Mastermind 29171 points

    Hello Davide,

    SPI communication is 100% digital. You should not see sinusoidal waveforms on the SPI pins on any device (TI or Arduino). Double check your Arduino setup and make sure you are correctly grounding your scope probes.

    Regarding the issue with communication with the wireless transmitter, I would double check the phase and clock polarity configuration on the TI MCU. Please review the waveforms in the TI SPI documentation carefully. Every device manufacturer uses a different definition for SPI mode; you should not assume mode X on TI device is the same as mode X on your transceiver.  

  • 0 in reply to Gus Martinez
    Prodigy 10 points

    First of all, thanks for the attention and the answer. Actually, after some further testing, we reached out the conclusion that is not some communication problem, cause it seems to perfectly communicate and change the state of the SX1276 transceiver between SLEEP and STAND-BY. Instead, when it comes to put TX mode (transimission state after having loaded data into the registers of the transceiver), nothing happens and it lays in the previous state. So i don't think could be a polarity or phase issue, 'cause i've also checked it out. After some surf in the internet in some forums, someone pointed the issue to power supply, but i don't think it's the cause either, having tested with an external power supplier. I can't figure out why it just can't go in transmission mode

  • 0 in reply to Davide Frasson
    TI__Mastermind 29171 points

    Davide, understood. Since the SPI communication between the MCU and the transceiver appears to be working correctly, I am closing this thread. If you have further questions about the MCU SPI itself, please feel free to post here or open a new thread.