Hardware Connections
NOTE
The RSSIE bit in Echo register COMMAND must be set to 1 to enable the
entire RSSI module before RSSI measurements can be made.
•
•
RSSIC—Outputs an analog indication of the RSSI. This can be sampled with an MCU ADC to
obtain greater accuracy or faster sampling than possible with Echo’s internal conversion. The
driver can be configured to use an MCU ATD module to read analogue RSSI measurements.
NOTE
Applications can enable the RSSI module, set RSSIC high of their own
accord, and use an ADC directly without driver intervention.
DATACLK—Can be used to provide the MCU with an accurate clock source for generating the
output waveforms for transmission. This is useful on MCUs that use a low-accuracy clock, such as
an RC oscillator.
The driver can be configured to allow Echo to output DATACLK and to use this signal as an
external clock input for the timer.
•
•
STROBE—Can be used to control power by turning Echo on and off when in receive mode. See
Section 5, “Reducing Power Consumption,” for more information.
ENABLEPA—This signal can be used on Freescale’s Echo RF modules to control an additional
external amplification stage on the output transmission. When ENABLEPA is 1, the power
amplifier is enabled. When ENABLEPA is 0, the power amplifier is disabled. The driver can be
configured to ignore ENABLEPA.
•
ENABLELNA—This signal can be used on Freescale’s Echo RF modules to control an additional
external amplification stage on the received signal. When ENABLELNA is 1, the low noise
amplifier is enabled. When ENABLELNA is 0, the low noise amplifier is disabled. The driver can
be configured to ignore ENABLELNA.
6.1
MCU Resources Required
The hardware connection diagram shown in Figure 4 illustrates the required and optional resources that
the driver can be configured to use.
•
Required resources:
— SPI—SPI connections for communication with and configuration of Echo.
— Timer channel—A single timer channel must be completely under driver control, including the
associated channel I/O pin. The driver must be linked to the channel interrupt vector as well.
NOTE
The driver must be able to initialize the timer modulus for the timer
containing the channel; it cannot then be altered.
— Three I/O pins—General-purpose I/O pins are required for configuration of Echo. SEB and
CONFB are required.
Software Drivers for MC33696, Rev. 1
8
Freescale Semiconductor
FREESCALE [ Freescale ]
