flowchart

每个gnuradio的程序都是一个通信系统，是一个流图。

from gnuradio import gr, blocks, filter, analog

class my_topblock(gr.top_block):
     def __init__(self):
        gr.top_block.__init__(self)
        amp = 1
        taps = filter.firdes.low_pass(1, 1, 0.1, 0.01)
        self.src = analog.noise_source_c(analog.GR_GAUSSIAN, amp)
        self.flt = filter.fir_filter_ccf(1, taps)
        self.snk = blocks.null_sink(gr.sizeof_gr_complex)
        self.connect(self.src, self.flt, self.snk)
if __name__ == "__main__":
     tb = my_topblock()
     #tb.run()
     tb.start()
     tb.wait()

__init__初始化之后，tb.start()开始运行，tb.wait()相当于thread.join()，等待tb运行结束才加入新的线程。

或者使用tb.run()，启动流图。

运行时更新flowchart

在通信系统运行的时候，经常需要根据输入信号改变系统的状态，这时候需要更新流图。更新流图有三步：

1. 锁定，停止运行，处理数据
2. 更新
3. 解锁

from gnuradio import gr, analog, blocks
import time
class mytb(gr.top_block):
    def __init__(self):
        gr.top_block.__init__(self)
        self.src0 = analog.noise_source_c(analog.GR_GAUSSIAN, 1)
        self.src1 = analog.noise_source_c(analog.GR_GAUSSIAN, 1)
        self.add = blocks.add_cc()
        self.sub = blocks.sub_cc()
        self.head = blocks.head(gr.sizeof_gr_complex, 1000000)
        self.snk = blocks.file_sink(gr.sizeof_gr_complex, "output.32fc")
        self.connect(self.src0, (self.add,0))
        self.connect(self.src1, (self.add,1))
        self.connect(self.add, self.head)
        self.connect(self.head, self.snk)

def main():
    tb = mytb()
    tb.start()
    time.sleep(0.01)
    # Stop flowgraph and disconnect the add block
    tb.lock()
    tb.disconnect(tb.add, tb.head)
    tb.disconnect(tb.src0, (tb.add,0))
    tb.disconnect(tb.src1, (tb.add,1))
    # Connect the sub block and restart
    tb.connect(tb.sub, tb.head)
    tb.connect(tb.src0, (tb.sub,0))
    tb.connect(tb.src1, (tb.sub,1))
    tb.unlock()
    tb.wait()
 if __name__ == "__main__":
     main()