CC2500
SWRS040C
Page 26 of 89
The
GDO0
pin can also be used for an on-chip
analog temperature sensor. By measuring the
voltage on the
GDO0
pin with an external ADC,
the
temperature
can
be
calculated.
Specifications for the temperature sensor are
found in Section 4.7 on page 14.
With default
register setting (0x7F) the
temperature sensor output is only available
when the frequency synthesizer is enabled
(e.g. the MANCAL, FSTXON, RX and TX
states).
It is necessary to write 0xBF to the
register to use the analog temperature
sensor in the IDLE state. Before leaving the
IDLE state, the
register should be
restored to its default value (0x7F).
11.3
Optional Radio Control Feature
The
CC2500
has an optional way of controlling
the radio, by reusing
SI
,
SCLK
and
CSn
from
the SPI interface. This feature allows for a
simple three-pin control of the major states of
the radio: SLEEP, IDLE, RX and TX.
This optional functionality is enabled with the
configuration bit.
State changes are commanded as follows:
When
CSn
is high the
SI
and
SCLK
is set to
the desired state according to Table 18. When
CSn
goes low the state of
SI
and
SCLK
is
latched and a command strobe is generated
internally according to the control coding. It is
only
possible
to
change
state
with
this
functionality. That means that for instance RX
will not be restarted if
SI
and
SCLK
are set to
RX and
CSn
toggles. When
CSn
is low the
SI
and
SCLK
has normal SPI functionality.
All pin control command strobes are executed
immediately, except the
strobe, which is
delayed until
CSn
goes high.
CSn
SCLK
SI
Function
1
X
X
Chip unaffected by
SCLK
/
SI
0
0
Generates
SPWD
strobe
0
1
Generates
STX
strobe
1
0
Generates
SIDLE
strobe
1
1
Generates
SRX
strobe
0
SPI
mode
SPI
mode
SPI mode (wakes up into
IDLE if in SLEEP/XOFF)
Table 18: Optional Pin Control Coding
12 Data Rate Programming
The data rate used when transmitting, or the
data rate expected in receive is programmed
by
the
and
the
configuration
registers.
The data rate is given by the formula below.
As the formula shows, the programmed data
rate depends on the crystal frequency.
XOSC
E
DRATE
DATA
f
M
DRATE
R
28
_
2
2
_
256
The following approach can be used to find
suitable values for a given data rate:
256
2
2
_
2
log
_
_
28
20
2
E
DRATE
XOSC
DATA
XOSC
DATA
f
R
M
DRATE
f
R
E
DRATE
If
is rounded to the nearest integer
and becomes 256, increment
and
use
=0.
The data rate can be set from 1.2 kBaud to
500 kBaud with the minimum step size of:
Min Data
Rate
[kBaud]
Typical
Data Rate
[kBaud]
Max Data
Rate
[kBaud]
Data Rate
Step Size
[kBaud]
0.8
1.2/2.4
3.17
0.0062
3.17
4.8
6.35
0.0124
6.35
9.6
12.7
0.0248
12.7
19.6
25.4
0.0496
25.4
38.4
50.8
0.0992
50.8
76.8
101.6
0.1984
101.6
153.6
203.1
0.3967
203.1
250
406.3
0.7935
406.3
500
500
1.5869
Table 19: Data Rate Step Size
Содержание CC2500
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