^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) =====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) Kernel driver max6875
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) =====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) Supported chips:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) * Maxim MAX6874, MAX6875
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) Prefix: 'max6875'
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) Addresses scanned: None (see below)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) Datasheet: http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) Author: Ben Gardner <bgardner@wabtec.com>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) Description
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) -----------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) It provides timed outputs that can be used as a watchdog, if properly wired.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) It also provides 512 bytes of user EEPROM.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) At reset, the MAX6875 reads the configuration EEPROM into its configuration
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) registers. The chip then begins to operate according to the values in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) registers.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) The Maxim MAX6874 is a similar, mostly compatible device, with more inputs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) and outputs:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) =========== === === ====
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) - vin gpi vout
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) =========== === === ====
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) MAX6874 6 4 8
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) MAX6875 4 3 5
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) =========== === === ====
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) See the datasheet for more information.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) Sysfs entries
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) -------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) eeprom - 512 bytes of user-defined EEPROM space.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) General Remarks
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) ---------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) Valid addresses for the MAX6875 are 0x50 and 0x52.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) Valid addresses for the MAX6874 are 0x50, 0x52, 0x54 and 0x56.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) The driver does not probe any address, so you explicitly instantiate the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) devices.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) Example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) $ modprobe max6875
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) $ echo max6875 0x50 > /sys/bus/i2c/devices/i2c-0/new_device
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) addresses. For example, for address 0x50, it also reserves 0x51.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) The even-address instance is called 'max6875', the odd one is 'dummy'.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) Programming the chip using i2c-dev
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) ----------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) Use the i2c-dev interface to access and program the chips.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) Reads and writes are performed differently depending on the address range.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) The configuration registers are at addresses 0x00 - 0x45.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) Use i2c_smbus_write_byte_data() to write a register and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) i2c_smbus_read_byte_data() to read a register.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) The command is the register number.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) Examples:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) To write a 1 to register 0x45::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) i2c_smbus_write_byte_data(fd, 0x45, 1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) To read register 0x45::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) value = i2c_smbus_read_byte_data(fd, 0x45);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) The configuration EEPROM is at addresses 0x8000 - 0x8045.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) The user EEPROM is at addresses 0x8100 - 0x82ff.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) Use i2c_smbus_write_word_data() to write a byte to EEPROM.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) The command is the upper byte of the address: 0x80, 0x81, or 0x82.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) The data word is the lower part of the address or'd with data << 8::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) cmd = address >> 8;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) val = (address & 0xff) | (data << 8);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) Example:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) To write 0x5a to address 0x8003::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) i2c_smbus_write_word_data(fd, 0x80, 0x5a03);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) Reading data from the EEPROM is a little more complicated.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) Use i2c_smbus_write_byte_data() to set the read address and then
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) i2c_smbus_read_byte() or i2c_smbus_read_i2c_block_data() to read the data.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) Example:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) To read data starting at offset 0x8100, first set the address::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) i2c_smbus_write_byte_data(fd, 0x81, 0x00);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) And then read the data::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) value = i2c_smbus_read_byte(fd);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) or::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) count = i2c_smbus_read_i2c_block_data(fd, 0x84, 16, buffer);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) The block read should read 16 bytes.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) 0x84 is the block read command.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) See the datasheet for more details.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136)
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