Tool/software:
Hi folks,
I am encountering a problem regarding the setting of the CS absolulte threshold in Async mode, which is a must for compatibility with various old devices.
In my application, I need to set the threshold dynamically according to the relevant settings the usesr are using .
The datasheet presents tables of "Typical RSSI Value in dBm at CS Threshold" at only 2.4kBaud and 250kBaud.
stating that "For other data rates, the user must generate similar tables to find the CS absolute threshold." So I could assume that the main factor influencing the CS threshold is the data rate.
To find out the difference in CS threshold between different data rates, I did some tests with two CC1101 modules connected to Smart RF Studio via a CC debugger.
To make it simple, I used the same MAX_LNA_GAIN / MAX_DVGA_GAIN / MAGN_TARGET / CARRIER_SENSE_ABS_THR, and just changed the data rates.
By configuring the GDO0 to 0x0E, and GDO2 to 0x0D on RX, I can monitor the signals with a logic analyzer, and record the RSSI value shown on the Smart RF Studio when the CS asserts on GDO0.
Here is a table showing the rough values I obtained:
| Settings | Data rate(kBaud) | CARRIER_SENSE_ABS_THR | RSSI at CS threshold | ||||||
|
868Mhz / GFSK Dev/BW aligned with settings Optimized for sensitivity on Smart RF Studio
|
1.2 | 0 | -94 | ||||||
| 2.4 | 0 | -94 | |||||||
| 4.8 | 0 | -98 | |||||||
| 10 | 0 | -98 | |||||||
| 38.4 | 0 | -99 | |||||||
| 76.8 | 0 | -94 | |||||||
| 100 | 0 | -94 | |||||||
| 250 | 0 | -93 |
I asked my client for the full list of the data rates at which the user will set CC1101 to operate, but they are unknow for now, so I can't decide for which data rates I should generate the tables,
however, there is a statement my client made in his reply :
I think it is possible to optimize the transceiver settings at maximum speed.
Since we need to use the transceiver in asynchronous mode to measure pulse durations.
This makes me a little confused. As I am a novice in transceiver development, I've been doing some research to gain a conprehensive understanding, and came accross a post :
I am kinda inspired by Sverre's reply:
My question is:
If I program the CC1101 to a higher data rate (say 250kBaud) than the actual operating rate(say 100kBaud) for jitter ruduction, which data rate should I consider using when finding the CS threshold?
Thank you for your support and insights!