User manual

© 2011 Microchip Technology Inc. DS70656A-page 21
PLM_FEC
This setting enables the Forward Error Correction (FEC) feature. Please note that the
Viterbi algorithm used for the FEC feature requires significant processing power, espe-
cially at higher code constraint lengths. At a carrier frequency of 129.6 kHz, no room is
left to run FEC and this option must be disabled.
PLM_QUALITY_MEASURE
This setting enables received signal quality estimation and determines a 16-bit quality
metric calculated during the initial bytes after the last byte synchronization has been
found. The metric is an average value of absolute values of demodulated signal sam-
ples, taken in the instance of bit decisions during the first 16 bytes after byte
synchronization has been found. A value greater then 0x7F00 means perfect quality.
PLM_LOCAL_ECHO
This setting, if enabled, allows the modem to receive its own transmissions.
PLM_DEBUG_MODE
This setting enables various debugging modes and normally should be off (set to
DEBUG OFF). The other modes supported are:
Signal Logging mode, where signal samples on various demodulation stages can
be saved in a circular buffer
Performance Measurement mode in which a GPIO pin (RG0) is set high
whenever the processor is executing low-level modem code
PLM_RAM_SAVING
If enabled, this setting causes the modem code to use less RAM (reduced by a third)
at a cost of consuming more processing power (2 to 4 MIPS). In case this option is
enabled, a processing buffer size must also be selected by manually setting
PLM_DEM_BLOCK_LEN. The smaller the buffer, the smaller the amount of RAM used;
however, the performance hit is more significant.
PLM_ADC
This setting allows the selection of the ADC, in case the dsPIC33F DSC device used
has more than one ADC module.
PLM_USE_DMA
This setting, if set to ‘
1’, causes the code to be compiled with DMA support. Unless
there are good reasons not to (e.g., no DMA support in the selected CPU model), DMA
should be used for best performance.
PLM_FC
This setting sets the carrier frequency and must not be changed while using the
daughter board.
PLM_BAUD
This setting sets the modem baud rate. Available options are: 1200, 2400, 3600, 4800,
5400, and 7200 (default).