BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 1 | Kernel driver max6875 |
| 2 | ===================== |
| 3 | |
| 4 | Supported chips: |
Jean Delvare | 089bd86 | 2005-06-23 23:37:53 +0200 | [diff] [blame] | 5 | * Maxim MAX6874, MAX6875 |
| 6 | Prefix: 'max6875' |
bgardner@wabtec.com | 93ffa43 | 2005-07-12 13:21:50 -0500 | [diff] [blame] | 7 | Addresses scanned: None (see below) |
Jean Delvare | 089bd86 | 2005-06-23 23:37:53 +0200 | [diff] [blame] | 8 | Datasheet: |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 9 | http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf |
| 10 | |
| 11 | Author: Ben Gardner <bgardner@wabtec.com> |
| 12 | |
| 13 | |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 14 | Description |
| 15 | ----------- |
| 16 | |
Jean Delvare | 089bd86 | 2005-06-23 23:37:53 +0200 | [diff] [blame] | 17 | The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor. |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 18 | It provides timed outputs that can be used as a watchdog, if properly wired. |
| 19 | It also provides 512 bytes of user EEPROM. |
| 20 | |
Jean Delvare | 089bd86 | 2005-06-23 23:37:53 +0200 | [diff] [blame] | 21 | At reset, the MAX6875 reads the configuration EEPROM into its configuration |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 22 | registers. The chip then begins to operate according to the values in the |
| 23 | registers. |
| 24 | |
Jean Delvare | 089bd86 | 2005-06-23 23:37:53 +0200 | [diff] [blame] | 25 | The Maxim MAX6874 is a similar, mostly compatible device, with more intputs |
| 26 | and outputs: |
Jean Delvare | 089bd86 | 2005-06-23 23:37:53 +0200 | [diff] [blame] | 27 | vin gpi vout |
| 28 | MAX6874 6 4 8 |
| 29 | MAX6875 4 3 5 |
| 30 | |
bgardner@wabtec.com | 93ffa43 | 2005-07-12 13:21:50 -0500 | [diff] [blame] | 31 | See the datasheet for more information. |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 32 | |
| 33 | |
| 34 | Sysfs entries |
| 35 | ------------- |
| 36 | |
bgardner@wabtec.com | 93ffa43 | 2005-07-12 13:21:50 -0500 | [diff] [blame] | 37 | eeprom - 512 bytes of user-defined EEPROM space. |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 38 | |
| 39 | |
| 40 | General Remarks |
| 41 | --------------- |
| 42 | |
bgardner@wabtec.com | 93ffa43 | 2005-07-12 13:21:50 -0500 | [diff] [blame] | 43 | Valid addresses for the MAX6875 are 0x50 and 0x52. |
| 44 | Valid addresses for the MAX6874 are 0x50, 0x52, 0x54 and 0x56. |
| 45 | The driver does not probe any address, so you must force the address. |
| 46 | |
| 47 | Example: |
| 48 | $ modprobe max6875 force=0,0x50 |
| 49 | |
| 50 | The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple |
| 51 | addresses. For example, for address 0x50, it also reserves 0x51. |
bgardner@wabtec.com | 0283fe6 | 2005-07-27 12:43:21 -0500 | [diff] [blame^] | 52 | The even-address instance is called 'max6875', the odd one is 'max6875 subclient'. |
bgardner@wabtec.com | 93ffa43 | 2005-07-12 13:21:50 -0500 | [diff] [blame] | 53 | |
| 54 | |
| 55 | Programming the chip using i2c-dev |
| 56 | ---------------------------------- |
| 57 | |
| 58 | Use the i2c-dev interface to access and program the chips. |
bgardner@wabtec.com | 0283fe6 | 2005-07-27 12:43:21 -0500 | [diff] [blame^] | 59 | Reads and writes are performed differently depending on the address range. |
bgardner@wabtec.com | 93ffa43 | 2005-07-12 13:21:50 -0500 | [diff] [blame] | 60 | |
| 61 | The configuration registers are at addresses 0x00 - 0x45. |
| 62 | Use i2c_smbus_write_byte_data() to write a register and |
| 63 | i2c_smbus_read_byte_data() to read a register. |
| 64 | The command is the register number. |
| 65 | |
| 66 | Examples: |
| 67 | To write a 1 to register 0x45: |
| 68 | i2c_smbus_write_byte_data(fd, 0x45, 1); |
| 69 | |
| 70 | To read register 0x45: |
| 71 | value = i2c_smbus_read_byte_data(fd, 0x45); |
| 72 | |
| 73 | |
| 74 | The configuration EEPROM is at addresses 0x8000 - 0x8045. |
| 75 | The user EEPROM is at addresses 0x8100 - 0x82ff. |
| 76 | |
| 77 | Use i2c_smbus_write_word_data() to write a byte to EEPROM. |
| 78 | |
| 79 | The command is the upper byte of the address: 0x80, 0x81, or 0x82. |
| 80 | The data word is the lower part of the address or'd with data << 8. |
| 81 | cmd = address >> 8; |
| 82 | val = (address & 0xff) | (data << 8); |
| 83 | |
| 84 | Example: |
| 85 | To write 0x5a to address 0x8003: |
| 86 | i2c_smbus_write_word_data(fd, 0x80, 0x5a03); |
| 87 | |
| 88 | |
| 89 | Reading data from the EEPROM is a little more complicated. |
| 90 | Use i2c_smbus_write_byte_data() to set the read address and then |
| 91 | i2c_smbus_read_byte() or i2c_smbus_read_i2c_block_data() to read the data. |
| 92 | |
| 93 | Example: |
| 94 | To read data starting at offset 0x8100, first set the address: |
| 95 | i2c_smbus_write_byte_data(fd, 0x81, 0x00); |
| 96 | |
| 97 | And then read the data |
| 98 | value = i2c_smbus_read_byte(fd); |
| 99 | |
| 100 | or |
| 101 | |
| 102 | count = i2c_smbus_read_i2c_block_data(fd, 0x84, buffer); |
| 103 | |
| 104 | The block read should read 16 bytes. |
| 105 | 0x84 is the block read command. |
| 106 | |
| 107 | See the datasheet for more details. |
BGardner@Wabtec.com | c3bc4ca | 2005-06-03 13:03:27 -0400 | [diff] [blame] | 108 | |