1 =====================
2 Kernel driver max6875
3 =====================
4
5 Supported chips:
6
7 * Maxim MAX6874, MAX6875
8
9 Prefix: 'max6875'
10
11 Addresses scanned: None (see below)
12
13 Datasheet: http://pdfserv.maxim-ic.com/en/
14
15 Author: Ben Gardner <bgardner@wabtec.com>
16
17
18 Description
19 -----------
20
21 The Maxim MAX6875 is an EEPROM-programmable po
22 It provides timed outputs that can be used as
23 It also provides 512 bytes of user EEPROM.
24
25 At reset, the MAX6875 reads the configuration
26 registers. The chip then begins to operate ac
27 registers.
28
29 The Maxim MAX6874 is a similar, mostly compati
30 and outputs:
31
32 =========== === === ====
33 - vin gpi vout
34 =========== === === ====
35 MAX6874 6 4 8
36 MAX6875 4 3 5
37 =========== === === ====
38
39 See the datasheet for more information.
40
41
42 Sysfs entries
43 -------------
44
45 eeprom - 512 bytes of user-defined EEPR
46
47
48 General Remarks
49 ---------------
50
51 Valid addresses for the MAX6875 are 0x50 and 0
52
53 Valid addresses for the MAX6874 are 0x50, 0x52
54
55 The driver does not probe any address, so you
56 devices.
57
58 Example::
59
60 $ modprobe max6875
61 $ echo max6875 0x50 > /sys/bus/i2c/devices/i
62
63 The MAX6874/MAX6875 ignores address bit 0, so
64 addresses. For example, for address 0x50, it
65 The even-address instance is called 'max6875',
66
67
68 Programming the chip using i2c-dev
69 ----------------------------------
70
71 Use the i2c-dev interface to access and progra
72
73 Reads and writes are performed differently dep
74
75 The configuration registers are at addresses 0
76
77 Use i2c_smbus_write_byte_data() to write a reg
78 i2c_smbus_read_byte_data() to read a register.
79
80 The command is the register number.
81
82 Examples:
83
84 To write a 1 to register 0x45::
85
86 i2c_smbus_write_byte_data(fd, 0x45, 1);
87
88 To read register 0x45::
89
90 value = i2c_smbus_read_byte_data(fd, 0x45);
91
92
93 The configuration EEPROM is at addresses 0x800
94
95 The user EEPROM is at addresses 0x8100 - 0x82f
96
97 Use i2c_smbus_write_word_data() to write a byt
98
99 The command is the upper byte of the address:
100 The data word is the lower part of the address
101
102 cmd = address >> 8;
103 val = (address & 0xff) | (data << 8);
104
105 Example:
106
107 To write 0x5a to address 0x8003::
108
109 i2c_smbus_write_word_data(fd, 0x80, 0x5a03);
110
111
112 Reading data from the EEPROM is a little more
113
114 Use i2c_smbus_write_byte_data() to set the rea
115 i2c_smbus_read_byte() or i2c_smbus_read_i2c_bl
116
117 Example:
118
119 To read data starting at offset 0x8100, first
120
121 i2c_smbus_write_byte_data(fd, 0x81, 0x00);
122
123 And then read the data::
124
125 value = i2c_smbus_read_byte(fd);
126
127 or::
128
129 count = i2c_smbus_read_i2c_block_data(fd, 0x
130
131 The block read should read 16 bytes.
132
133 0x84 is the block read command.
134
135 See the datasheet for more details.
136
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