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drivers: Add SD card driver, controlled via SPI bus.
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‎drivers/sdcard/sdcard.py‎

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

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