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CC2538: Intermediate frequency (IF)

Mayte Penella
Prodigy 30 points
Part Number: CC2538
Other Parts Discussed in Thread: CC2590, Z-STACK

What is the Intermediate frequency (IF) of cc2538?

  • 0
    TI__Expert 6060 points

    Hi Mayte,

    I'm reaching out to the design team to identify that value. May I ask the reason that value is needed?

    Thanks,

    Jake

  • 0 in reply to Jake Pulliam
    Prodigy 30 points

    Hi Jake,

    We have a network working with Zigbee. Devices are installed on lampost between 4 m and 6 m high, all devices have direct visibility and distances are within 100 m or less. We have a CC2538 + CC2590 front end. CC2538 is working at 3 dBm. We tested more power but have the same issues.

    I am asking because we are having some devices that disconnect from the network at certain periods of time, at nights everything works fine but during the day the network does not work, some nodes are totally disconnected. We have tested several devices and interchanged from one location that works ok to the locations where the decive stops working. Devices at some locations always fail to connect during certain periods of time.

    We thought that there could be some interference but we have analyzed all the spectrum on site (at device level too) and there is no frequency that could be interfering in band. We have the front end, so we thought there could be some Intermodulation Distortion saturating the receiver at the intermediate frequency.

    Best regards,

    Mayte

  • 0 in reply to Mayte Penella
    TI__Guru**** 208557 points

    Hi Mayte,

    What Z-Stack version are you using, and what is the node type (ZC, ZR, ZED, ZNP)?  Have you tested 802.15.4 transmission quality of your custom board with Smart RF Studio, and verified the RF output levels to make sure that they match the expected configurations?  The CC2590 PA is superfluous if the TX power is 3 dBm given the CC2538 can reach a maximum output power of 7 dBm on its own.  Do you have a sniffer log that captures over-the-air behavior during network failure, and can you debug any devices to determine whether messages are not able to be sent by the device?

    Regards,
    Ryan

  • 0 in reply to Jake Pulliam
    Prodigy 30 points

    Hi Jake, were you able to check this?

    BR

  • 0 in reply to Mayte Penella
    TI__Expert 6060 points

    Hi Mayte,

    TX can be zero IF but can also be set to other values via MDMTEST1.TX_TONE register. You can read back that value using SmartRF studio. See https://www.ti.com/lit/ug/swru319c/swru319c.pdf for the full register descriptions.

    RX is 1 MHz at data rates up to 1Mbps and 0 IF for 2 Mbps

    Jake

  • 0
    Prodigy 30 points

    Hi Jake,

    I meant the frequency at which the demodulator lowers the received RF signal to process it. The register you are referring to is used to transmit a baseband tone, but I cannot see any value for the IF frequency. I do not think this is a programmable value.

    Thanks

    Mayte

  • 0 in reply to Mayte Penella
    TI__Expert 6060 points

    Hi Mayte,

    as per the TRM, For TX "if MDMTEST1.MOD_IF is 0 the tone is superpositioned on the modulated data, effectively giving modulation with an IF".

    For the receive you are correct, it's not a programable value, it's not shown in the TRM but as noted above RX IF is 1MHz at data rates up to 1 Mbps and zero IF for 2Mbps.