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关于CC1120 RSSI/CS Timing Diagram的问题

Other Parts Discussed in Thread: CC1175

根据文档SWRU295E -《CC112X/CC1175 Low-Power High Performance Sub-1 GHz RF Transceivers/Transmitter User’s Guide》第38页,有图Figure 16: RSSI/CS Timing Diagram。

问题1:

        AGC的仅仅是在射频发射机从IDLE转RX状态之后的T0+T1+T2时间内更新(如果这个过程中没有返回IDLE状态,则不会触发AGC再次更新) ?

        还是AGC会一直周期性地更新?

问题2:

根据上图描述RSSI_UPDATE时间与CARRIER_SENSE时序一致,这个CARRIER_SENSE是否就是CS response time?

但是文档SWRU295E的40-41页又有以下公式。这两者有何区别?

根据SWRU295E第41页,有如下说明:

To guarantee that the RSSI measurement is done during the packet and not on noise, preamble + sync word should be greater than twice the RSSI update rate.

问题3:

     是否意味着preamble + sync word的时间可以根据CS response time来调整(由于官方提供了DN510 CS Response Time 的计算工具)?

  • 需要讨论一下,会尽快过来回复
  • 好的,谢谢!
  • 目前相关工程师复活节休假去了,此问题还在pending状态,后续有更新再来
  • 回复如下:

    1) The AGC will start with max gain and will update x number of times, depending on the signal strength received.

    The figure is meant to show the carrier sense response time and other RSSI related signal in two cases (two different RSSI_VALID_COUNT) in a situation where you would receive a fairly weak signal (only 1 gain reduction)

    2) The carrier sense response time will tell you when the carrier sense is valid (assertion of CARRIER_SENSE_VALID). This corresponds to the first RSSI_UPDATE. After that, the CARRIER_SENSE_VALID will be asserted as long as the device is in RX mode, but the CARRIER_SENSE signal will/can go high/low after that, depending on the signal strength. CARRIER_SENSE will be updated on RSSI_UPDATE.

    3) Not sure I understand the question. The RSSI update rate = T2*(2RSSI_VALID_CNT + 1).

    Usually you use a 4 byte long sync word, so you need to make sure that your preamble is long enough so that:

    (# preamble bits + 32)/data rate > 2*( RSSI update rate)
  • 非常感谢。关于问题1,我们这边还是希望能够得到答复确认一下。

    问题1:

            AGC的仅仅是在射频发射机从IDLE转RX状态之后的T0+T1+T2时间内更新(如果这个过程中没有返回IDLE状态,则不会触发AGC再次更新) ?

            还是AGC会一直周期性地更新?