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本科毕业设计外文文献翻译
题 目：Packet Handling Hardware Support 学生姓名： 学 院： 系 别： 专 业： 班 级： 指导教师：
二 〇 一 四 年 六 月
Packet Handling Hardware Support
参考文献：Texas Instruments.CC1101 Low-Power Sub-1 GHz RF Transceiver.www. ti.com. 2013
The CC1101 has built-in hardware support for packet oriented radio protocols. In transmit mode, the packet handler can be configured to add the following elements to the packet stored in the TX FIFO:
? A programmable number of preamble bytes
? A two byte synchronization (sync) word. Can be duplicated to give a 4-byte
sync word (recommended). It is not possible to only insert preamble or only insert a sync word
? A CRC checksum computed over the data field.
The recommended setting is 4-byte preamble and 4-byte sync word, except for 500 kBaud data rate where the recommended preamble length is 8 bytes. In addition, the following can be implemented on the data field and the optional 2-byte CRC checksum:
? Whitening of the data with a PN9 sequence
? Forward Error Correction (FEC) by the use of interleaving and coding of the
data (convolutional coding)
In receive mode, the packet handling support will de-construct the data packet by implementing the following (if enabled):
? Preamble detection ? Sync word detection
? CRC computation and CRC check ? One byte address check
? Packet length check (length byte checked against a programmable maximum
length) ? De-whitening
? De-interleaving and decoding
Optionally, two status bytes (see Table 27 and Table 28) with RSSI value, Link Quality Indication, and CRC status can be appended in the RX FIFO.
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Table 27: Received Packet Status Byte 1(first byte appended after the data) Bit Field Name Description 7:0 RSSI RSSI value Table 28: Received Packet Status Byte 2(second byte appended after the data) Bit Field Name Description 7 CRC_OK 1:CRC for received data OK (or CRC disabled) 0:CRC error in received data 6:0 Indicating the link quality Note: Register fields that control the packet handling features should only be altered when CC1101 is in the IDLE state. LQI 1. Data whitening
From a radio perspective, the ideal over the air data are random and DC free. This results in the smoothest power distribution over the occupied bandwidth. This also gives the regulation loops in the receiver uniform operation conditions (on data dependencies).
Real data often contain long sequences of zeros and ones. In these cases, performance can be improved by whitening the data before transmitting, and de-whitening the data in the receiver.
With CC1101, this can be done automatically. By setting PKTCTRLO. WHITE_DATA=1, all data, except the preamble and the sync word will be XOR-ed with a 9-bit pseudo-random (PN9) sequence before being transmitted. This is shown in Figure 16. At the receiver end, the data are XOR-ed with the same pseudorandom sequence. In this way, the whitening is reversed, and the original data appear in the receiver. The PN9sequence is initialized to all 1’s.
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2. Packet Format
The format of the data packet can be configured and consists of the following items (see Figure 17):
? Preamble
? Synchronization word ? Optional length byte ? Optional address byte ? Payload
? Optional 2 byte CRC
The preamble pattern is an alternating sequence of ones and zeros (10101010…). The minimum length of the preamble is programmable through the value of MDMCFG1.NUM_PREAMBLE. When enabling TX, the modulator will start transmitting the preamble. When the programmed number of preamble bytes has been
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