Texas Instruments RF430F5978EVM, User Manual, Page: 13 / 31

Content Start Length Command Voltage
(mV)
Temperature
(ºC)
LF RSSI X
(dBm)
LF RSSI Y
(dBm)
LF RSSI Z
(dBm)
LF
Wake
UHF RSSI
(1)
UHF LQI
(2)
EOL
Example:
01 0A 01 087E 00EA A3 AD CA 08 24 B0 0D
Explanation: Start of
Telegram
Without
(start,
length,
Cmd
and
EOL)
byte
Response
always Null
Byte
Representing
voltage
0x087E
=>
2174 mV
Representing
temperature
0x00EA
=>
23.4°C
Representing
LF RSSI X
0xA3
=>
163 dBm
Representing
LF RSSI Y
0xAD
=>
173 dBm
Representing
LF RSSI Y
0xCA
=>
202 dBm
Which
wake up
occurred
8 =>
Wake A
Representing
UHF RSSI
0x24
=>
-54 dBm
Representing
UHF LQI EST
0xB0 & 0x7F
=>
48
EOL End
of
Message
1 byte 1 byte 1 byte 2 byte 2 byte 1 byte 1 byte 1 byte 1 byte 1 byte 1 byte 1byte
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LF Wake-Up Mode Tab
3. Received data on UHF antenna at wake up mode. If no data is available, reports "ND".
Table 2. Received Data Examples
(1) UHF RSSI
The UHF RSSI value read from the RSSI status register is a 2s-complement number. The following
procedure can be used to convert the RSSI reading to an absolute power level (RSSI_dBm)
1. Read the RSSI status register
2. Convert the reading from a hexadecimal number to a decimal number (RSSI_dec)
3. If RSSI_dec
≥
128 then RSSI_dBm = (RSSI_dec – 256)/2 – RSSI_offset
4. If RSSI_dec < 128 then RSSI_dBm = (RSSI_dec)/2 – RSSI_offset
Refer to the device-specific data sheet for typical RSSI offset values and for typical RSSI values vs
input power levels at various frequencies.
The RF430F5978EVM power condition meets following regulations:
FCC 5.231
ETSSI 300 220
ETSSI 300 330
ETSSI 301 489
(2) Link Quality Indicator (LQI)
The Link Quality Indicator is a metric of the current quality of the received signal. If
PKTCTRL1.APPEND_STATUS is enabled, the value is automatically added to the last byte
appended after the payload. The value can also be read from the LQI status register. The LQI gives
an estimate of how easily a received signal can be demodulated by accumulating the magnitude of
the error between ideal constellations and the received signal over the 64 symbols immediately
following the sync word. LQI is best used as a relative measurement of the link quality (a low value
indicates a better link than what a high value does), because the value is dependent on the
modulation format. (Mask out bit7, as LQI = bit6 to bit0)
4. USB Interface status displays the status of USB connection Access point and MRD2.
• Access Point:
– Virtual com port, module serial number, frequency band, CW PA, firmware version
– Not found: No access point available
• Reader (MRD2) :
– Virtual com port, firmware version
– Not found: No Micro Reader 2 available
5. Temperature and VCC graphical display
• The red line represents RF430F5978EVM VCC module voltage.
• The green line represents RF430F5978EVM module temperature.
Continuous mode displays the last 50 packets.
13 SLRU007 – July 2014 RF430F5978EVM User Guide
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