CC1200: CCA_STATUS clarification

user4734074

Part Number: CC1200

Hi,

I am confusing about CCA_STATUS and CARRIER_SENSE signal shown in fig 16, pp38 in SWRU346B.

1) If CCA mode is "indicate clear channel when RSSI is below threshold", is CCA_STATUS same as CARRIER_SENSE?

2) Is the decision of TXONCCA done at every RSSI update timing?

3) If I need "CCA listening time" which consists of some RSSI update period, do I check every CCA_STATUS during the CCA listening time?

(What I am thinking is that if at least one RSSI period in CCA listening time is more than threshold, CCA result is busy.)

Thank you.

over 7 years ago

0 Siri over 7 years ago

TI__Guru* 87011 points

Hi

1)
The signals are not the same.
CCA_STATUS is low if the channel is busy and high otherwise. If a channel is interpreted as busy or not depends on the PKT_CFG2.CCA_MODE
CARRIER_SENSE is high if the RSSI is above a programmable threshold and low otherwise. CARRIER_SENSE_VALID must be asserted before this CARRIER_SENSE signal is checked.

2)
This depends on which CCA mode you are using.
For ordinary CCA (no LBT) you do a check once when STX is strobed.
TXONCCA_FAILED is asserted if CCA_STATUS is low and we continue in RX
TXONCCA_FAILED is cleared if CCA_STATUS is high and we continues to TX
3)
If you want to achieve this I think you need to set CCA_MODE = 0 and then do the check manually. Once you are in RX you wait for CARRIER_SENSE_VALID and you read the CARRIER_SENSE signal. The CARRIER_SENSE signal will be updated when the RSSI is updated (timing depends on RSSI_VALID_COUNT, see figure 16 in the user guide: http://www.ti.com/lit/swru346 )

BR
Siri

0 user4734074 over 7 years ago in reply to Siri

Prodigy 130 points

Dear Siri
Thank you very much for your detail explanation!

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CC1200: CCA_STATUS clarification