Modify LimeSDR FPGA

The LimeSDR-USB allows to either transmit signals at once or schedule them. In all cases the samples must be passed from the host to the device at each call, which can take time due to the USB speed and latency. We would like to be able to just tell the device to transmit a specific type of signal, either at once or at a specific timestamp, without passing the samples each time. The different signals to transmit could have been uploaded to the device previously (the LimeSDR-USB already allows to upload one, but its usage is limited) , or perhaps the device itself could generate them. This would require modifying the FPGA, as well as some of the C APIs to either add or expand existing functions.