Function Headers and Description
When the driver fills an Rx buffer, it sets the full flag to signify the buffer contains a message. The
application must clear the full flag to return the buffer to the pool and be available to receive more
messages. The next message will not be returned to the application until the previous message is released.
9.5.5
Checksum
Although not included in the buffer, the checksum is calculated and automatically sent with messages by
the driver software. To maintain compatibility with the Tango and Romeo device drivers, the checksums
sent and received are calculated over the ID, length, and data bytes.
The checksum provides a minimal error detection mechanism. The checksum bit in the Rx buffer indicates
that a checksum error has been detected. This is set to 1 on error and cleared otherwise.
9.5.6
Bank Flag
If both banks are active, this bit indicates which bank received the message.
9.5.7
RSSI
If the automatic RSSI reading is enabled (by calling Echo_EnableRSSI()), the RSSI of incoming messages
is automatically measured and stored with the messages. The 5 bit RSSI value is the sum of the upper and
lower 4-bit portions of the Echo RSSI register value. If necessary, this can be used to calculate the signal
strength in dBm.
If the automatic RSSI reading is disabled, the RSSI value will not be present with the message. The RSSI
flag bit indicates whether there is a valid RSSI measurement for this message; the RSSI flag is set to 1 if
the RSSI bits contain a valid measurement.
10 Function Headers and Description
10.1 Initialization and Startup Functions
10.1.1 Echo_Initialize
void Echo_Initialize(void)
Syntax:
Parameters: None
Return:
None
Software Drivers for MC33696, Rev. 1
18
Freescale Semiconductor
FREESCALE [ Freescale ]
