EMC2101 stand-alone

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socratease
 
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EMC2101 stand-alone

Post by socratease »

I was hoping to use the EMC2101 in stand-alone applications like in a power supply fan upgrade, but I can't seem to get it to work. First of all, the configuration registers get reset to their defaults every time the power is cycled, which makes it hard to use for this application without adding another controller for the fan controller.

The datasheet section 4.9 does say that you can put an EEPROM chip on the I2C bus, and the EMC2101 is supposed to load the configuration from it on power-up. So I bought some 24LC02B chips, put one of them on the bus, and programmed my preferred configuration into it with my Bus Pirate. But on power-up the EMC2101 still had default values in the configuration registers. I put a logic analyzer and then a scope on the I2C bus to see what was going wrong, but there is no indication I can see that the EMC2101 makes any attempt to read an external device after power-up like the datasheet says it should.

Has anybody else had experience trying to program the EMC2101 from EEPROM?

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adafruit_support_mike
 
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Re: EMC2101 stand-alone

Post by adafruit_support_mike »

As a sanity check, do you have pull-up resistors on the SDA and SCL lines?

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socratease
 
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Re: EMC2101 stand-alone

Post by socratease »

I'm powering the Vin pin of the breakout board with 3.3v, that powers the I2C pull-up resistors on the board. Scope and analyzer show both bus lines going high.

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Re: EMC2101 stand-alone

Post by adafruit_support_mike »

Okay, what value do you get for the device ID?

Only the EMC2101-R supports EEPROM configuration, and it needs a pull-up resistor on the /ALERT-TACH pin to select autoprogramming. See table 5.1 on page 21 of the datasheet.

The standard EMC2101 device ID is 0x16. The EMC2101-R's ID is 0x28.

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socratease
 
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Re: EMC2101 stand-alone

Post by socratease »

I hadn't realized there was two versions, my bad. There *is* a pull-up on the ALERT pin, but there's no -R suffix on the part number on the case. I'm accessing it with address 0x4c. My datasheet doesn't show any address other than that (section 4.7) but I think you might be looking at a different datasheet since our page numbers don't line up.

Anyway, if it's not a -R part, that would certainly explain why it isn't trying to access the EEPROM.

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Re: EMC2101 stand-alone

Post by adafruit_support_mike »

The product ID is stored in register 0xFD. It's different from the I2C address.

The next register (0xFE) is the manufacturer ID (should be 0x5D), and the register after that (0xFF) is the revision number.

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