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Documentation/misc-devices/max6875
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Kernel driver max6875 ===================== Supported chips: |
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* Maxim MAX6874, MAX6875 Prefix: 'max6875' |
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Addresses scanned: None (see below) |
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Datasheet: |
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http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf Author: Ben Gardner <bgardner@wabtec.com> |
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Description ----------- |
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The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor. |
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It provides timed outputs that can be used as a watchdog, if properly wired. It also provides 512 bytes of user EEPROM. |
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At reset, the MAX6875 reads the configuration EEPROM into its configuration |
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registers. The chip then begins to operate according to the values in the registers. |
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The Maxim MAX6874 is a similar, mostly compatible device, with more intputs and outputs: |
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vin gpi vout MAX6874 6 4 8 MAX6875 4 3 5 |
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See the datasheet for more information. |
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Sysfs entries ------------- |
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eeprom - 512 bytes of user-defined EEPROM space. |
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General Remarks --------------- |
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Valid addresses for the MAX6875 are 0x50 and 0x52. Valid addresses for the MAX6874 are 0x50, 0x52, 0x54 and 0x56. |
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The driver does not probe any address, so you explicitly instantiate the devices. |
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Example: |
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$ modprobe max6875 $ echo max6875 0x50 > /sys/bus/i2c/devices/i2c-0/new_device |
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The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple addresses. For example, for address 0x50, it also reserves 0x51. |
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The even-address instance is called 'max6875', the odd one is 'dummy'. |
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Programming the chip using i2c-dev ---------------------------------- Use the i2c-dev interface to access and program the chips. |
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Reads and writes are performed differently depending on the address range. |
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The configuration registers are at addresses 0x00 - 0x45. Use i2c_smbus_write_byte_data() to write a register and i2c_smbus_read_byte_data() to read a register. The command is the register number. Examples: To write a 1 to register 0x45: i2c_smbus_write_byte_data(fd, 0x45, 1); To read register 0x45: value = i2c_smbus_read_byte_data(fd, 0x45); The configuration EEPROM is at addresses 0x8000 - 0x8045. The user EEPROM is at addresses 0x8100 - 0x82ff. Use i2c_smbus_write_word_data() to write a byte to EEPROM. The command is the upper byte of the address: 0x80, 0x81, or 0x82. The data word is the lower part of the address or'd with data << 8. cmd = address >> 8; val = (address & 0xff) | (data << 8); Example: To write 0x5a to address 0x8003: i2c_smbus_write_word_data(fd, 0x80, 0x5a03); Reading data from the EEPROM is a little more complicated. Use i2c_smbus_write_byte_data() to set the read address and then i2c_smbus_read_byte() or i2c_smbus_read_i2c_block_data() to read the data. Example: To read data starting at offset 0x8100, first set the address: i2c_smbus_write_byte_data(fd, 0x81, 0x00); And then read the data value = i2c_smbus_read_byte(fd); or |
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count = i2c_smbus_read_i2c_block_data(fd, 0x84, 16, buffer); |
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The block read should read 16 bytes. 0x84 is the block read command. See the datasheet for more details. |
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