I am working on a project using the Robostix and a Verdex pro, and I am
having some strange issues with the i2c level converter (9515A) on the
Robostix. From what I am able to determine, I have Robostix boards from two
different batches with two different version of this chip.
I have one regular robostix board (with headers) that has a chip labeled:
There is no manufacturer logo on the chip. This board seems to work fine
and I have been using it for about 2 weeks with no troubles.
I recently ordered 3 robostix boards with no headers (robostix-th) and it
has a different chip on it with a TI emblem labeled:
I assume this is the TI version of the 9515A. However, it seems very flakey
and does not work most of the time. I have loaded the i2c-test hex file on
the gumstix and can communicate with it. Probing the I2C lines on the 5
volt side of the converter (at the UARTS header location) the signals follow
what is commanded from the gumstix. However, when I attach a micro-clip and
a multimeter to the 3.3V side of the 9515, I only get valid signal levels
out part of the time. Often, the output will simply stick at 1 or 0.
Sometimes, however, the output follows the output from the 5 volt side of
the chip as it should. I have checked the VCC5 rail and it appears to be
correct and at 5 volts. I also have tried a second Robostix board with the
same IC, and it exhibits the same behavior.
My question: Does anyone know of a reason the IC was changed, and has
anyone had problems with the TI version of the I2C level shifter? If
someone could tell me the vendor of the chip that I mention first, I am
willing to replace the TI chip with one that works.