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Ensure that the chip select line is low between the read command, #1

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merged 1 commit into from
Sep 27, 2017
Merged

Ensure that the chip select line is low between the read command, #1

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20 changes: 13 additions & 7 deletions adafruit_sdcard.py
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Original file line number Diff line number Diff line change
Expand Up @@ -221,14 +221,14 @@ def _cmd(self, cmd, arg=0, crc=0, response_buf=None, data_block=True, wait=True)
return buf[0]
return -1

def _block_cmd(self, cmd, block, crc):
def _block_cmd(self, cmd, block, crc, response_buf=None):
"""Issue a command to the card with a block argument.

:param int cmd: The command number.
:param int block: The relevant block.
:param int crc: The crc to allow the card to verify the command and argument."""
if self._cdv == 1:
return self._cmd(cmd, block, crc)
return self._cmd(cmd, block, crc, response_buf=response_buf)

# create and send the command
buf = self._cmdbuf
Expand All @@ -242,6 +242,7 @@ def _block_cmd(self, cmd, block, crc):
buf[4] = 0
buf[5] = crc

result = -1
with self._spi as spi:
self._wait_for_ready(spi)

Expand All @@ -251,8 +252,13 @@ def _block_cmd(self, cmd, block, crc):
for i in range(_CMD_TIMEOUT):
spi.readinto(buf, end=1, write_value=0xff)
if not (buf[0] & 0x80):
return buf[0]
return -1
result = buf[0]
break

if response_buf != None and result == 0:
self._readinto(response_buf)

return result

def _cmd_nodata(self, cmd, response=0xff):
"""Issue a command to the card with no argument.
Expand Down Expand Up @@ -340,10 +346,10 @@ def readblocks(self, start_block, buf):
assert nblocks and not err, 'Buffer length is invalid'
if nblocks == 1:
# CMD17: set read address for single block
if self._block_cmd(17, start_block, 0) != 0:
# We use _block_cmd to read our data so that the chip select line
# isn't toggled between the command, response and data.
if self._block_cmd(17, start_block, 0, response_buf=buf) != 0:
return 1
# receive the data
self._readinto(buf)
else:
# CMD18: set read address for multiple blocks
if self._block_cmd(18, start_block, 0) != 0:
Expand Down