PCからFT245RL経由でSDメモリーカードにSPIでアクセスしてみる(初期化まで)

でインストール．

SDメモリカードをSPI接続で叩くコードを書く．
参考:
http://elm-chan.org/docs/mmc/mmc.html
http://naruken.cweb.tk/labo/mmc/index.html

from pylibftdi import BitBangDevice, Bus
import time

class sd(object):
    """
    The FT245R is wired to the SD as follows:
       DB0 to DI
       DB1 to D0
       DB2 to CLK
       DB3 to CS
    """
    DI = Bus(0)
    DO = Bus(1)
    CLK = Bus(2)
    CS = Bus(3)
    POW = Bus(4)

    def __init__(self, device):
        # The Bus descriptor assumes we have a 'device'
        # attribute which provides a port
        self.device = device

    def _trigger(self):
        "generate a L->H->L"
        self.CLK = 0
        self.CLK = 1
        self.CLK = 0

    def init_spi(self):
        print "power on and wait > 1ms"
        self.POW = 1
        time.sleep(0.01)

        print "dummy clock >= 74 with CS and DI high"
        self.CS = 1
        self.DI = 1
        for _ in range(74): #more than 74 times
            self._trigger()

        print "CMD0 with CS low"
        self.CS = 0
        self.write_cmd(0, 0, 0b1001010)

        print "-> wait response for 0-8 byte"
        while 1:
            if self.read_r1() == 0b1:
                print "cmd0 ok (response == 1)"
                break

        #while cmd1
        print "cmd1"
        while 1:
            self.write_cmd(1, 0, 0)
            if self.read_r1() == 0b0:
                break
        print "cmd1 ok (res == 0)"

    def _write_raw(self, byte):
        for i in range(8):
            self.DI = (byte >> (7-i)) & 0b1
            print "%d" % self.DI,
            self._trigger()
        print

    def write_cmd(self, cmd, addr, crc): #cmd 6bit, addr 8x4bit, crc7bit
        #cmd
        self._write_raw(0b01000000 + cmd)
        #addr
        for i in range(4):
        self._write_raw((addr >> (3-i)*8) & 0xff)
        #CRC
        self._write_raw(0b1 + (crc << 1))
        #up
        self.DI = 1
        #print "DI after cmd: ", self.DI

    def read_r1(self):
        print "read_r1 (timeout >= 8 byte)"
        for i in range(8*8):
            do = self.DO
            self._trigger()
            print "%d" % do,
            if (do == 0):
                break
            if (i==10*8-1):
                print "timeout"
                exit()

        #print "DO is 0"
        res = 0
        for i in range(7):
            res += self.DO << (6-i)
            self._trigger()

        print "response:", res
        return res

def display(device_id=None):

    with BitBangDevice(device_id) as bb:

        # the actual baudrate
        # is 16x this in bitbang mode...
        bb.baudrate = 19200 #19200, 9600, 4800
        bb.direction = 0b00011101
        bb.port = 0x00 #output (not pullup)
        sdc = sd(bb)
        sdc.init_spi()
        print "complete init"


if __name__ == '__main__':
    import sys
    display()

power on and wait > 1ms
dummy clock >= 74 with CS and DI high
CMD0 with CS low
0 1 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
1 0 0 1 0 1 0 1
-> wait response for 0-8 byte
read_r1 (timeout >= 8 byte)
1 1 1 1 1 1 1 1 0 response: 1
cmd0 ok (response == 1)
cmd1
0 1 0 0 0 0 0 1
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
read_r1 (timeout >= 8 byte)
1 1 1 1 1 1 1 1 0 response: 1
0 1 0 0 0 0 0 1
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
read_r1 (timeout >= 8 byte)
1 1 1 1 1 1 1 1 0 response: 0
cmd1 ok (res == 0)
complete init