blob: 7c003b9e654ad2ba0e8bf8433fc46946cc87f37c [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.
import array
import logging
import usb
import stm32usb
"""Accesses I2C buses through stm32 usb endpoint."""
class Si2cError(Exception):
"""Class for exceptions of Si2c."""
def __init__(self, msg, value=0):
"""Si2cError constructor.
Args:
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(object):
"""I2C bus class to access devices on the bus.
Usage:
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, serialname=None):
self._logger = logging.getLogger("Si2c")
self._logger.debug("")
self._port = port
self._susb = stm32usb.Susb(vendor=vendor, product=product,
interface=interface, serialname=serialname, logger=self._logger)
self._logger.debug("Set up stm32 i2c")
def __del__(self):
"""Si2c destructor."""
self._logger.debug("Close")
def 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.
Args:
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.
Interface:
write: [addr, write_count, read_count, data ... ]
read: [data .. ]
Returns:
Bytes read from i2c.
Raises:
Si2cError on transaction failure.
"""
self._logger.debug("Si2c.wr_rd("
"slave_address=0x%x, write_list=%s, read_count=%s)" % (
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)
read_count = max(0, read_count)
# Send wr_rd command to stm32.
cmd = [self._port, slave_address, write_length, read_count] + write_list
ret = self._susb._write_ep.write(cmd, self._susb.TIMEOUT_MS)
# Read back response if necessary.
bytes = self._susb._read_ep.read(read_count + 4, self._susb.TIMEOUT_MS)
if len(bytes) < (read_count + 4):
raise Si2cError("Read status failed.")
if bytes[0] != 0 or bytes[1] != 0:
raise Si2cError("Read status failed: 0x%02x%02x" % (bytes[1], bytes[0]))
self._logger.debug("Si2c.wr_rd result 0x%02x%02x, read %s" % (bytes[1], bytes[0], bytes[4:]))
return bytes[4:]