CC1350: Reducing Transmit Delay

Devin Kelly

Part Number: CC1350

Hello,

I have a signal generator generating a square wave at about 2 kHz. I've connected the siggen to a CC1350 GPIO pin (pin 25) and I've got the CC1350 transmitting based on the rising edge.

Looking at my scope I see that the packet from the CC1350 comes 110 µs after the rising edge from the siggen. It's very consistent and I can't get the 110 µs to change no matter what I do.

Here's how I've configured the CC1350:

    typedef struct
    {
        uint32_t reserved:2;   // unused
        uint32_t inputMode:2;  //0:  rising, 1: falling, 2: both edges
        uint32_t reserved2:4;  // unused
        uint32_t source:5;     // 22: RFC_GPI0, 23: RFC_GPI1
    } ExternalTrigger;

    // Set the trigger configuration
    ExternalTrigger triggerConfig =
    {
        .inputMode = 2,       // both edges
        // .inputMode = 0,       // rising edge, SWCU185D pg 1910
        .source = 22          // Use RFC_GPI0, corresponds to PINCC26XX_setMux
    };

    PINCC26XX_setMux(pinHandle, IOID_25, PINCC26XX_MUX_RFC_GPI0);

    RF_cmdPropTxAdv.pktLen = PAYLOAD_LENGTH;
    RF_cmdPropTxAdv.pPkt = packet;
    RF_cmdPropTxAdv.startTime = *((uint32_t*)&triggerConfig);
    RF_cmdPropTxAdv.startTrigger.triggerType = TRIG_EXTERNAL

over 5 years ago

0 IUsedToBeARealPerson (M-W) over 5 years ago

TI__Guru 58425 points

Hi Devin,

There is a delay between trigger and "data on air". This is in the ballpark of what you are seeing and it include things such as calibrating the synthesizer (if needed) and preparing the internal TX buffers in the RF core etc.

0 Devin Kelly over 5 years ago in reply to IUsedToBeARealPerson (M-W)

Prodigy 110 points

So there's no way to reduce this delay?

0 IUsedToBeARealPerson (M-W) over 5 years ago in reply to Devin Kelly

TI__Guru 58425 points

Hi David,

There might be solutions (more or less practical) to get a "quicker" responds but it is very situation depend. To be aale to provide good advice on what could be done here I would need to know more about what you are aiming for more specifically. Could you elaborate on the use-case here, like in expectations for the RF part, power consumption of the solution etc?

If you could also share some more code and the setup of the TX commands that would be helpful for me to understand just how you use the radio and how you set it up (it is clear that you do external triggers but not much else).

Sub-1 GHz

Sub-1 GHz forum

CC1350: Reducing Transmit Delay