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CC1101 modulation schemes.

charith mendis
Prodigy 90 points
Other Parts Discussed in Thread: CC1101, TEST2

What will be a good modulation scheme to use if my application needs high noise immunity,  and needs up to 64 channels in the range 902 - 928 MHz ? Can somebody recommend me any? The current channel spacing is near the maximum possible with channel BW of 58 kHz. 

  • 0
    TI__Mastermind 36395 points

    Charith, 

    For multi channel applications in the 902-928MHz band, the recommended modulation scheme is GFSK. GFSK is also the recommended modulation scheme used in SmartRFStudio 7.0. Personally, I have found the 38.4kb/s settings to work very well. 

    /TA

  • 0 in reply to TA12012
    Prodigy 90 points

    thanks!!

    I will try it out and let you know.

  • 0 in reply to charith mendis
    Prodigy 90 points

    1.I used GFSK, but the receiver detects erroneous packets even when the transmitter is off. I then tried with no modulation, then the receiver only detects packets when the transmitter transmits. What I mean by detect is that the MSP430 detects a falling edge interrupt on the GDO0 pin of the CC1101.

    Following are my registry settings.

    FREQ2 0x22

    FREQ1 0xC4

    FREQ0 0xEC

    MDMCFG0 0xA0

    MDMCFG4 0xBA

    MDMCFG3 0x83

    MDMCFG1 0x13

    MDMCFG2 0x92

    DEVIATN 0x47  

    Following are the resulting characteristics I want to achieve.

    channel BW 116 kHz

    channel spacing 330 kHz

    starting frequency 904 MHz

    no of channels used 64

    ending frequency 925MHz MHz

    modulation format GFSK

    freqency devaition in mod format 47.6 kHz

    data rate 38.4 kbaud/s  

     

    Are my settings correct or is it a problem with my settings? Can you recommend me a modulation scheme hierarchy to try out in order?

     

    2.Secondly, I want to know whether I can use a packet sniffer software like Smart RF studio for the basic development kit CC1101DK-EM868. Will I need an expansion kit and will there be a compatibility issue?

     

    Thanks in advance.

  • 0 in reply to charith mendis
    TI__Mastermind 36395 points

    Charith,

    The receiver will wake up from time to time saying the is a packet, but there is nothing. This is due to the syncword being only 32 bits long, you will get a 1/2^32 change of the sync word being correct when the reciever is on. But in almost all cases the CRC check will fail and your can make a simple algorithm to discard those packets.

    I do see some weird stuff when I type your values into SmartRF studio, it looks like you are using 800kHz RX bandwidth and only 0.01kb/s. So here are the setings that I have used.

    # Deviation = 20.629883
    # Base frequency = 903.999878
    # Carrier frequency = 903.999878
    # Channel number = 0
    # Carrier frequency = 903.999878
    # Modulated = true
    # Modulation format = GFSK
    # Manchester enable = false
    # Sync word qualifier mode = 30/32 sync word bits detected
    # Preamble count = 4
    # Channel spacing = 199.951172
    # Carrier frequency = 903.999878
    # Data rate = 38.3835
    # RX filter BW = 101.562500
    # Data format = Normal mode
    # Length config = Variable packet length mode. Packet length configured by the first byte after sync word
    # CRC enable = true
    # Packet length = 255
    # Device address = 0
    # Address config = No address check
    # CRC autoflush = false
    # PA ramping = false
    # TX power = 0
    IOCFG0 = 0x06
    FSCTRL1 = 0x06
    FREQ2 = 0x22
    MDMCFG4 = 0xCA
    MDMCFG3 = 0x83
    MDMCFG2 = 0x13
    DEVIATN = 0x35
    MCSM0 = 0x18
    FOCCFG = 0x16
    AGCCTRL2 = 0x43
    WORCTRL = 0xFB
    FSCAL3 = 0xE9
    FSCAL2 = 0x2A
    FSCAL1 = 0x00
    FSCAL0 = 0x1F
    TEST2 = 0x81
    TEST1 = 0x35
    TEST0 = 0x09
    PA_TABLE0 = 0xC0

    Thomas

  • 0 in reply to TA12012
    Prodigy 90 points

    thanks I will try it out.

    Can I use SmartRF studio for any development kit as I mentioned in the previous post? Can I use it as a standalone application to determine config values?

    Still I haven't used it. 

    Can I use it to physically check packet transfers. I only have a CC1101-DK_EM868 and a MSP430 evaluation board. What are the additional hardware that I will need?

    Can I use smartRFStudio for packet sniffing?

    It would be highly appreciated if you can answer these promptly as I am a newbie at this. 

  • 0 in reply to charith mendis
    TI__Mastermind 36395 points

    Charith, 

    Yes, SmartRF Studio is designed to be used as a demostration tool. It comes with basics settings and basic packet error rate test software.

    You need the entire kit as show in this link for it to work with CC1101 family of transceivers.

    http://focus.ti.com/graphics/tool/CC1101DK868-915.jpg

    And you can use smartRF studio for packet sniffing (basic functions only, it will not decode the information for you, it will just display it)

    /TA