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"""
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 on pyboard:
import pyb, sdcard, os
sd = sdcard.SDCard(pyb.SPI(1), pyb.Pin.board.X5)
pyb.mount(sd, '/sd2')
os.listdir('/')
Example usage on ESP8266:
import machine, sdcard, os
sd = sdcard.SDCard(machine.SPI(0), machine.Pin(15))
os.umount()
os.VfsFat(sd, "")
os.listdir()
"""
from micropython import const
import time
_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)
_TOKEN_CMD25 = const(0xfc)
_TOKEN_STOP_TRAN = const(0xfd)
_TOKEN_DATA = const(0xfe)
class SDCard:
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_spi(self, baudrate):
try:
master = self.spi.MASTER
except AttributeError:
# on ESP8266
self.spi.init(baudrate=baudrate, phase=0, polarity=0)
else:
# on pyboard
self.spi.init(master, baudrate=baudrate, phase=0, polarity=0)
def init_card(self):
# init CS pin
self.cs.init(self.cs.OUT, value=1)
# init SPI bus; use low data rate for initialisation
self.init_spi(100000)
# clock card at least 100 cycles with cs high
for i in range(16):
self.spi.write(b'\xff')
# CMD0: init card; should return _R1_IDLE_STATE (allow 5 attempts)
for _ in range(5):
if self.cmd(0, 0, 0x95) == _R1_IDLE_STATE:
break
else:
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.init_spi(1320000)
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):
time.sleep_ms(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.write(buf)
# wait for the response (response[7] == 0)
for i in range(_CMD_TIMEOUT):
response = self.spi.read(1, 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.write(b'\xff')
if release:
self.cs.high()
self.spi.write(b'\xff')
return response
# timeout
self.cs.high()
self.spi.write(b'\xff')
return -1
def cmd_nodata(self, cmd):
self.spi.write(cmd)
self.spi.read(1, 0xff) # ignore stuff byte
for _ in range(_CMD_TIMEOUT):
if self.spi.read(1, 0xff)[0] == 0xff:
self.cs.high()
self.spi.write(b'\xff')
return 0 # OK
self.cs.high()
self.spi.write(b'\xff')
return 1 # timeout
def readinto(self, buf):
self.cs.low()
# read until start byte (0xff)
while self.spi.read(1, 0xff)[0] != 0xfe:
pass
# read data
mv = self.dummybuf_memoryview[:len(buf)]
self.spi.write_readinto(mv, buf)
# read checksum
self.spi.write(b'\xff')
self.spi.write(b'\xff')
self.cs.high()
self.spi.write(b'\xff')
def write(self, token, buf):
self.cs.low()
# send: start of block, data, checksum
self.spi.read(1, token)
self.spi.write(buf)
self.spi.write(b'\xff')
self.spi.write(b'\xff')
# check the response
if (self.spi.read(1, 0xff)[0] & 0x1f) != 0x05:
self.cs.high()
self.spi.write(b'\xff')
return
# wait for write to finish
while self.spi.read(1, 0xff)[0] == 0:
pass
self.cs.high()
self.spi.write(b'\xff')
def write_token(self, token):
self.cs.low()
self.spi.read(1, token)
self.spi.write(b'\xff')
# wait for write to finish
while self.spi.read(1, 0xff)[0] == 0x00:
pass
self.cs.high()
self.spi.write(b'\xff')
def count(self):
return self.sectors
def readblocks(self, block_num, buf):
nblocks, err = divmod(len(buf), 512)
assert nblocks and not err, 'Buffer length is invalid'
if nblocks == 1:
# 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)
else:
# CMD18: set read address for multiple blocks
if self.cmd(18, block_num * self.cdv, 0) != 0:
return 1
offset = 0
mv = memoryview(buf)
while nblocks:
self.readinto(mv[offset : offset + 512])
offset += 512
nblocks -= 1
return self.cmd_nodata(b'\x0c') # cmd 12
return 0
def writeblocks(self, block_num, buf):
nblocks, err = divmod(len(buf), 512)
assert nblocks and not err, 'Buffer length is invalid'
if nblocks == 1:
# CMD24: set write address for single block
if self.cmd(24, block_num * self.cdv, 0) != 0:
return 1
# send the data
self.write(_TOKEN_DATA, buf)
else:
# CMD25: set write address for first block
if self.cmd(25, block_num * self.cdv, 0) != 0:
return 1
# send the data
offset = 0
mv = memoryview(buf)
while nblocks:
self.write(_TOKEN_CMD25, mv[offset : offset + 512])
offset += 512
nblocks -= 1
self.write_token(_TOKEN_STOP_TRAN)
return 0
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