blob: 1dc93f5b818ff95196be22b5bcb67945be4b4bb2 [file] [log] [blame]
# Copyright 2016 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Accesses I2C buses through stm32 usb endpoint."""
import array
import errno
import logging
import usb
import i2c_base
import stm32usb
_MAX_WRITE_SIZE = (1 << 12) - 1
_MAX_READ_SIZE = (1 << 15) - 1
class Si2cError(Exception):
"""Class for exceptions of Si2c."""
def __init__(self, msg, value=0):
"""Si2cError constructor.
msg: string, message describing error in detail
value: integer, value of error when non-zero status returned. Default=0
super(Si2cError, self).__init__(msg, value)
self.msg = msg
self.value = value
class Si2cBus(i2c_base.BaseI2CBus):
"""I2C bus class to access devices on the bus.
bus = Si2cBus()
# read 1 byte from slave(0x48) register(0x16)
bus.wr_rd(0x48, [0x16], 1)
# write 2 bytes to slave(0x48) register(0x20)
bus.wr_rd(0x48, [0x20, 0x01, 0x02])
Instance Variables:
_logger: Si2c tagged log output
_port: stm32 i2c controller index
_susb: stm32 usb class
def __init__(self, vendor=0x18d1, product=0x501a, interface=1, port=0,
self._logger = logging.getLogger('Si2c')
self._port = port
self._logger.debug('Set port %d' % port)
self._susb = stm32usb.Susb(vendor=vendor, product=product,
interface=interface, serialname=serialname,
self._logger.debug('Set up stm32 i2c')
def reinitialize(self):
"""Reinitialize the usb endpoint"""
def _raw_wr_rd(self, slave_address, write_list, read_count=None):
"""Implements hdctools wr_rd() interface.
This function writes byte values list to I2C device, then reads
byte values from the same device.
slave_address: 7 bit I2C slave address.
write_list: list of output byte values [0~255].
read_count: number of byte values to read from device.
write: [addr, write_count, read_count, data ... ]
read: [data .. ]
Bytes read from i2c.
Si2cError on transaction failure.
'port=%d, slave_address=0x%x, write_list=%s, read_count=%s)' %
(self._port, slave_address, write_list, read_count))
# Clean up args from python style to correct types.
if not write_list:
write_list = []
write_length = len(write_list)
if write_length > _MAX_WRITE_SIZE:
raise Si2cError(
'requested write size %d exceeds the %d maximum supported by this '
'I2C-over-USB protocol' % (write_length, _MAX_WRITE_SIZE))
read_count = max(0, read_count)
if read_count > _MAX_READ_SIZE:
raise Si2cError(
'requested read size %d exceeds the %d maximum supported by this '
'I2C-over-USB protocol' % (read_count, _MAX_READ_SIZE))
# Encode the full write count across the multiple fields involved.
port_field = self._port | ((write_length >> 4) & 0xF0)
write_field = write_length & 0xFF
cmd = [port_field, slave_address, write_field]
# Encode the full read count across the multiple fields involved.
if read_count <= 0x7F:
cmd.append((read_count & 0x7F) | 0x80)
cmd.append((read_count >> 7) & 0xFF)
cmd.append(0) # reserved field
# Send wr_rd command to stm32.
ret = self._susb._write_ep.write(cmd, self._susb.TIMEOUT_MS)
except IOError as e:
if e.errno == errno.ENODEV:
self._logger.error('USB disconnected 0x%04x:%04x, servod failed.',
self._susb._vendor, self._susb._product)
# Read back response if necessary.
data = + 4, self._susb.TIMEOUT_MS)
if len(data) < (read_count + 4):
raise Si2cError('Read status failed.')
if data[0] != 0 or data[1] != 0:
raise Si2cError('Read status failed: 0x%02x%02x' % (data[1], data[0]))
self._logger.debug('Si2c.wr_rd result 0x%02x%02x, read %s' %
(data[1], data[0], data[4:]))
return data[4:]
def close(self):
"""Stm32i2c wind down logic.
Note: because servod runs in a thread, an exception gets thrown at the very
end unless we explicitly predelete this instance.
"""'Turning down STM32i2c interface.')
del self._susb
super(Si2cBus, self).close()