Wi.232FHSS-25/250-R™ Datasheet - Radiotronix - #39

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4.32. Receiver LNA Mode
regNVLNAMODE (0x24)
regLNAMODE (0x6F)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
D7
D6
D5
D4
D3
D2
D1
D0
7
6
5
4
3
2
1
0
Default Receiver LNA Mode: High Sensitivity (Wi.232FHSS-25), AGC Enabled (Wi.232FHSS-250-R)
By default, the Wi.232FHSS-25 module is configured for maximum receiver sensitivity. Similarly, the Wi.232FHSS-250-R is factory-configured to use its internal automatic gain control (AGC) circuit to manage receiver sensitivity. Reducing the gain increases the linearity of the receiver, but reduces maximum sensitivity; increasing the gain does the opposite. Generally speaking, higher linearity (increased third order input intercept point, IIP3) will give improved performance in high-interference environments; high gain yields better performance in low-interference environments.
The Wi.232FHSS-250-R contains an AGC circuit that manages these settings automatically, and it should be used whenever possible. However, when attempting to make RSSI measurements, fixing the LNA gain will produce more meaningful results.
The following table summarizes the LNA settings for each of the modules.
LNA Mode
WI.232FHSS-25-R
WI.232FHSS-250-R
Meaning
IIP3 Increase
Sensitivity Decrease
Meaning
IIP3 Increase
Sensitivity Decrease
0x00
High
Sensitivity
Reference
Reference
AGC Enabled
Variable
Variable
0x01
High Linearity
15 dB
10 dB
High
Sensitivity
Reference
Reference
0x02
Invalid
N/A
N/A
Mid Linearity
19.1 dB
6.5 dB
0x03
Invalid
N/A
N/A
High Linearity
41.8 dB
9.5 dB
Table 13, LNA Mode Settings
4.33. Compatibility Mode
regNVCOMPATMODE (0x25)
regCOMPATMODE (0x70)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
D7
D6
D5
D4
D3
D2
D1
D0
7
6
5
4
3
2
1
0
Default Compatibility Mode: Disabled (0x00)
The Wi.232FHSS-250-R operates at a much narrower receive bandwidth (200kHz) than the Wi.232FHSS-25 (600kHz). When the Wi.232FHSS-25 transmits, it deviates well outside the receiver bandwidth of the Wi.232FHSS-250-R. To address this problem, v1.0.5 and later Wi.232FHSS-25 firmware and all Wi.232FHSS-250-Rs support a compatibility mode. This allows both modules to communicate effectively with each other.
When enabled (0x01), compatibility mode reduces the maximum RF data rate to 76.8kbps, reduces the Wi.232FHSS-25's deviation to 80kHz, and reduces the Wi.232FHSS-25's receiving bandwidth to 200kHz. All UART baud rates are supported, although the RF data rates associated with baud rates 31250, 38400, 57600, and 115200 will be diminished.

pageCatalog pdf di En 2012-05-22-31