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There was recently a question that was raised on the RF link compatibility mode between a CC1101 and a CC1120; in which case CC1120 has its radio control and user interface designed based on the widely used CC1101 transceiver and the two shares the same command strobes and main radio states across the platforms. I had the time to research into the issue and identified a few similarity and differences between the two units; they are as described in this post.
Feel free to comment or provide additional inputs!
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The packet mode is indeed compatible between CC1101 and CC1120. A sample screenshot of the two packet format can be found in their respective datasheet or user’s guide as follows:
Both supports amplitude shift, frequency shift, and Gaussian shaped modulation formats including 2-(G)FSK, 4-FSK, OOK, ASK, as well as Minimum Shift Keying (MSK) modulation. They also support fixed- and variable- packet length mode that can be used for packets up to 255 bytes. For longer packets, infinite packet length mode is available. As for major differences between the two devices, they are as follows:
- Sync Word: CC1120 is variable to have 11-, 16-, 18-, 24-, or 32- bit synchronization word; CC1101 is set for 16- or 32- bit synchronization word
- Preamble: CC1120 can select from a minimal of 0 to 30 bytes preamble; CC1101 selects from 2 to 24 bytes
- Data Field: CC1120 has 128-byte RX and TX FIFOs; CC1101 has 64-byte RX and TX FIFOs
- Frequency Range: CC1120 and CC1101 supports frequency range as follows:
- Modulation: CC1120 supports 4-GFSK while CC1101 does not
- Channel Bandwidth: CC1120 has selectable channel bandwidth from 8 kHz à 200 kHz; CC1101 has it from 58 kHz à 812 kHz
- Data Rate: CC1120 and CC1101 supports the following datarate:
- Manchester Encoding: CC1120 performs encoding only on payload and CRC while CC1101 performs encoding on preamble, sync word, payload, CRC; as a result if the Manchester Encoding is used the following procedure needs to be implemented:
- Set PREAMBLE_CFG1. PREAMBLE_WORD to 10b or 11b
- Manually encode 2 bytes long sync word and write to SYNC[3:0]
Major features to note while establishing RF connection between mixed devices are data rate, frequency deviation, channel spacing, and modulation format. TI’s SmartRF Studio is a great tool to perform all the necessary register configurations on RF devices. The tool should prove to be easily operable and worthwhile. Users can simply open two different SmartRF Configuration tool windows for CC1101 and CC1120 respectively and configure the two channels to establish RF connection.
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Relevant Documents:
CC1120 Datasheet: http://www.ti.com/lit/ds/symlink/cc1120.pdf
CC112x/ CC1175 User’s Guide: http://www.ti.com/lit/ug/swru295c/swru295c.pdf
CC1101 Datasheet: http://www.ti.com/lit/ug/swru295c/swru295c.pdf
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Feel free to add additional comments or inputs!
Shiou Mei Huang
