According to the datasheet, "the RSSI_VALID status bit indicates when
the RSSI value is valid, meaning that the receiver has been enabled for
at least 8 symbol periods." Since receiving a packet will always be
longer than 8 symbol periods, there's no need to check. I think this
register should be checked when you're using CC2420 to sample background
noise.
-Han
Aleksandr N. Sadkov 提到:
Does CC2420 check the RSSI_VALID register before appending the RSSI value to
the last two bytes of the packet?
Regards, Aleksandr.
wbr, Sadkov Aleksandr
[EMAIL PROTECTED]
www.sumkino.com
www.wl.unn.ru
-----Original Message-----
From: Tsung-Han Lin [mailto:[EMAIL PROTECTED]
Sent: Monday, June 18, 2007 3:07 PM
To: Aleksandr N. Sadkov
Cc: [email protected]
Subject: Re: [Tinyos-help] RSSI measuring
RSSI value is measured by the radio chip. CC2420 will append the rssi,
crc and lqi to the last two bytes of the packet.
You can refer to the CC2420 datasheet:
http://www.chipcon.com/files/CC2420_Data_Sheet_1_3.pdf
-Han
Aleksandr N. Sadkov ??:
Hello All,
Could anybody explain how actually RSSI measured?
I mean where source code in TinyOS for reading of the RSSI.RSSI_VAL
register of the CC2420?
I found only code:
/task void receiveDone_task() {/
/ /
/ cc2420_header_t* header = getHeader( m_p_rx_buf );/
/ cc2420_metadata_t* metadata = getMetadata( m_p_rx_buf );/
/ //uint8_t* buf = (uint8_t*)header;/
/ //uint8_t length = buf[ 0 ];/
/ /
/ metadata->crc = buf[ length ] >> 7;/
/ metadata->rssi = buf[ length - 1 ];/
/ metadata->lqi = buf[ length ] & 0x7f;/
/ m_p_rx_buf = signal Receive.receive( m_p_rx_buf, m_p_rx_buf->data,
/
/ length );/
/ /
/ waitForNextPacket();/
/ /
/ }/
Could you explain why /buf[ length - 1 ]; /means RSSI/ ?/
/ /
Thank you, Aleksandr.
wbr, Sadkov Aleksandr
[EMAIL PROTECTED]
www.sumkino.com <http://www.sumkino.com>
www.wl.unn.ru
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