Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 4 of 4

Thread: teensy 3.2 and I2C EEPROM

  1. #1

    teensy 3.2 and I2C EEPROM

    Hello,

    I have a Teensy 3.2 and I am trying to duplicate this exercise
    https://www.pjrc.com/teensy/td_libs_Wire.html
    When I run this code, I get nothing, no output. I can run a I2C scanner code and retrieve the I2C address of the EEPROM
    in my case, it is 0x50 same as in the example above.

    I have a 24LC256 PDIP on my breadboard. as opposed to 24C256 in the example? not sure if that presents any issues?
    https://www.digikey.com/products/en/...=1&pageSize=25

    I wanted to make sure my I2C bus is in good order, so I placed a Adafruit MCP9808 pcb next in line
    and ran this I2C scanner utility to identify I2C addresses. 0x19
    https://gist.github.com/netmaniac/87...8e04bf1cbfde4a

    It seems to correctly identify I2C device addresses.. I also attached two MCP23017 further down the bus. (0x25 and 0x26)
    And their I2C addresses also appear with the scanner sketch.
    I have not yet tried doing anything more with the MCP23017. just connected to see the I2C addresses.

    I'm scratching my head over the EEPROM problem...
    My pull up resistors are 2.2K ohm.
    and I measure a voltage on SDA around 3.84V and SDC 3.84V and going up a little with pulses.

    and just for grins, I'm had the WP pin to both VIN and GND which seems to not affect anything.

    Appreciate any help or insight in solving this problem.


    Code:
    Starting I2C Scanner
    Scanning...
    I2C device found at address 0x19  !
    I2C device found at address 0x25  !
    I2C device found at address 0x26  !
    I2C device found at address 0x50  !
    done
    sample Adafruit temp output:

    Code:
    MCP9808 demo
    Found MCP9808!
    wake up MCP9808.... 
    Resolution in mode: 3
    Temp: 24.4375*C  and 75.9875*F.
    Shutdown MCP9808....
    Click image for larger version. 

Name:	eeprom.jpg 
Views:	7 
Size:	283.3 KB 
ID:	18230

  2. #2
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    10,106
    measure a voltage on SDA around 3.84V and SDC 3.84V
    Are those 5V parts? the pullups should show 3.3V to the T_3.2 as that device uses a 3.3V signal level for high. Pins may be 5V tolerant - but that isn't the same as working with 5V devices.

  3. #3
    Im not sure.. the data sheet says this about the 24LC256 :

    Click image for larger version. 

Name:	datasheet.jpg 
Views:	0 
Size:	36.2 KB 
ID:	18232

  4. #4
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    10,106
    Quote Originally Posted by random_number View Post
    Im not sure.. the data sheet says this about the 24LC256 :

    ...
    that looks like it should run at 3.3V

    The pullups should be to 3.3V and not register what was reported as 3.84V

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •