rp2_dma.py

import time
import uctypes
import struct
import machine

class DMA:
    DMA_BASE  = 0x50000000
    
    DMA_EN    = 0x01 << 0
    HIGH_PRIO = 0x01 << 1
    INCR_READ = 0x01 << 4
    INCR_WRITE= 0x01 << 5
    DREQ_PIO0_RX0 = 0x04 << 15
    DREQ_SPI1_TX  = 0x12 << 15
    DREQ_PERMANENT= 0x3F << 15
    IRQ_QUIET = 0x01 << 21
    BUSY      = 0x01 << 24
    
    def __init__( self, channelNumber ):
        offset = channelNumber * 0x40
        self.CHx_READ_ADDR     = DMA.DMA_BASE + 0x00 + offset
        self.CHx_WRITE_ADDR    = DMA.DMA_BASE + 0x04 + offset
        self.CHx_TRANS_COUNT   = DMA.DMA_BASE + 0x08 + offset
        self.CHx_CTRL_TRIG     = DMA.DMA_BASE + 0x0C + offset
    
    def config( self, src_addr, dst_addr, count, src_inc, dst_inc, trig_dreq ):
        machine.mem32[ self.CHx_CTRL_TRIG ]   = 0
        machine.mem32[ self.CHx_READ_ADDR ]   = src_addr
        machine.mem32[ self.CHx_WRITE_ADDR ]  = dst_addr
        machine.mem32[ self.CHx_TRANS_COUNT ] = count
        trig_val = 0
        if( src_inc ):
            trig_val |= DMA.INCR_READ
        if( dst_inc ):
            trig_val |= DMA.INCR_WRITE
        trig_val |= trig_dreq
        machine.mem32[ self.CHx_CTRL_TRIG ]   = trig_val
    
    def enable( self ):
        machine.mem32[ self.CHx_CTRL_TRIG ] |= DMA.DMA_EN
    
    def disable( self ):
        machine.mem32[ self.CHx_CTRL_TRIG ] = 0
    
    def is_busy( self ):
        if( machine.mem32[ self.CHx_CTRL_TRIG ] & DMA.BUSY ):
            return True
        else:
            return False

def test_dma():
    dma = DMA(0)
    src_buf = b"Hello World!"*1000
    dst_buf = bytearray( 12*1000 )
    
    dma.config( 
        src_addr = uctypes.addressof( src_buf ), 
        dst_addr = uctypes.addressof( dst_buf ),
        count = len( src_buf ), 
        src_inc = True, 
        dst_inc = True, 
        trig_dreq = DMA.DREQ_PERMANENT 
    )

    t0 = time.ticks_us()
    dma.enable()
    while( dma.is_busy() ):
        pass
    dma.disable()
    t1 = time.ticks_us()

    print( "dst", dst_buf[0:12], "..." )

    print( "Transfer speed [B/s]:", len( src_buf )/((t1-t0)*1e-6) )
    print( "@CPU freq:", machine.freq() )

if __name__=='__main__':
    test_dma()
    print( "done" )