diff options
Diffstat (limited to 'drivers/sdcard')
| -rw-r--r-- | drivers/sdcard/sdcard.py | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/drivers/sdcard/sdcard.py b/drivers/sdcard/sdcard.py new file mode 100644 index 0000000000..e51a594d8e --- /dev/null +++ b/drivers/sdcard/sdcard.py @@ -0,0 +1,202 @@ +""" +Micro Python driver for SD cards using SPI bus. + +Requires an SPI bus and a CS pin. Provides readblocks and writeblocks +methods so the device can be mounted as a filesystem. + +Example usage: + + import pyb, sdcard, os + sd = sdcard.SDCard(pyb.SPI(1), pyb.Pin.board.X5) + pyb.mount(sd, '/sd2') + os.listdir('/') + +""" + +import pyb + +class SDCard: + CMD_TIMEOUT = const(100) + + R1_IDLE_STATE = const(1 << 0) + #R1_ERASE_RESET = const(1 << 1) + R1_ILLEGAL_COMMAND = const(1 << 2) + #R1_COM_CRC_ERROR = const(1 << 3) + #R1_ERASE_SEQUENCE_ERROR = const(1 << 4) + #R1_ADDRESS_ERROR = const(1 << 5) + #R1_PARAMETER_ERROR = const(1 << 6) + + def __init__(self, spi, cs): + self.spi = spi + self.cs = cs + + self.cmdbuf = bytearray(6) + self.dummybuf = bytearray(512) + for i in range(512): + self.dummybuf[i] = 0xff + self.dummybuf_memoryview = memoryview(self.dummybuf) + + # initialise the card + self.init_card() + + def init_card(self): + # init CS pin + self.cs.high() + self.cs.init(self.cs.OUT_PP) + + # init SPI bus; use low data rate for initialisation + self.spi.init(self.spi.MASTER, baudrate=100000, phase=0, polarity=0) + + # clock card at least 100 cycles with cs high + for i in range(16): + self.spi.send(0xff) + + # CMD0: init card; should return R1_IDLE_STATE (allow 2 attempts) + if self.cmd(0, 0, 0x95) != R1_IDLE_STATE: + if self.cmd(0, 0, 0x95) != R1_IDLE_STATE: + raise OSError("no SD card") + + # CMD8: determine card version + r = self.cmd(8, 0x01aa, 0x87, 4) + if r == R1_IDLE_STATE: + self.init_card_v2() + elif r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND): + self.init_card_v1() + else: + raise OSError("couldn't determine SD card version") + + # get the number of sectors + # CMD9: response R2 (R1 byte + 16-byte block read) + if self.cmd(9, 0, 0, 0, False) != 0: + raise OSError("no response from SD card") + csd = bytearray(16) + self.readinto(csd) + if csd[0] & 0xc0 != 0x40: + raise OSError("SD card CSD format not supported") + self.sectors = ((csd[8] << 8 | csd[9]) + 1) * 2014 + #print('sectors', self.sectors) + + # CMD16: set block length to 512 bytes + if self.cmd(16, 512, 0) != 0: + raise OSError("can't set 512 block size") + + # set to high data rate now that it's initialised + self.spi.init(self.spi.MASTER, baudrate=1320000, phase=0, polarity=0) + + def init_card_v1(self): + for i in range(CMD_TIMEOUT): + self.cmd(55, 0, 0) + if self.cmd(41, 0, 0) == 0: + self.cdv = 512 + #print("[SDCard] v1 card") + return + raise OSError("timeout waiting for v1 card") + + def init_card_v2(self): + for i in range(CMD_TIMEOUT): + pyb.delay(50) + self.cmd(58, 0, 0, 4) + self.cmd(55, 0, 0) + if self.cmd(41, 0x40000000, 0) == 0: + self.cmd(58, 0, 0, 4) + self.cdv = 1 + #print("[SDCard] v2 card") + return + raise OSError("timeout waiting for v2 card") + + def cmd(self, cmd, arg, crc, final=0, release=True): + self.cs.low() + + # create and send the command + buf = self.cmdbuf + buf[0] = 0x40 | cmd + buf[1] = arg >> 24 + buf[2] = arg >> 16 + buf[3] = arg >> 8 + buf[4] = arg + buf[5] = crc + self.spi.send(buf) + + # wait for the repsonse (response[7] == 0) + for i in range(CMD_TIMEOUT): + response = self.spi.send_recv(0xff)[0] + if not (response & 0x80): + # this could be a big-endian integer that we are getting here + for j in range(final): + self.spi.send(0xff) + if release: + self.cs.high() + self.spi.send(0xff) + return response + + # timeout + self.cs.high() + self.spi.send(0xff) + return -1 + + def readinto(self, buf): + self.cs.low() + + # read until start byte (0xff) + while self.spi.send_recv(0xff)[0] != 0xfe: + pass + + # read data + mv = self.dummybuf_memoryview[:len(buf)] + self.spi.send_recv(mv, recv=buf) + + # read checksum + self.spi.send(0xff) + self.spi.send(0xff) + + self.cs.high() + self.spi.send(0xff) + + def write(self, buf): + self.cs.low() + + # send: start of block, data, checksum + self.spi.send(0xfe) + self.spi.send(buf) + self.spi.send(0xff) + self.spi.send(0xff) + + # check the response + if (self.spi.send_recv(0xff)[0] & 0x1f) != 0x05: + self.cs.high() + self.spi.send(0xff) + return + + # wait for write to finish + while self.spi.send_recv(0xff)[0] == 0: + pass + + self.cs.high() + self.spi.send(0xff) + + def count(self): + return self.sectors + + def readblocks(self, block_num, buf): + # TODO support multiple block reads + assert len(buf) == 512 + + # CMD17: set read address for single block + if self.cmd(17, block_num * self.cdv, 0) != 0: + return 1 + + # receive the data + self.readinto(buf) + return 0 + + def writeblocks(self, block_num, buf): + # TODO support multiple block writes + assert len(buf) == 512 + + # CMD24: set write address for single block + if self.cmd(24, block_num * self.cdv, 0) != 0: + return 1 + + # send the data + self.write(buf) + return 0 |