I2C Nightmare: So what's wrong with ASC?

hylee101001

Hi all,

I found out that the sensors I have been working on are all fine. I used another propeller board (not ASC) and it works fine. (which also implies that I threw some well-working sensors!! my money!)

Anyways, then, this fact tells me that the reason why I2C didn't work for my ASC is not because of voltage out of propeller pins (which is 3.3v) nor data transmit rate. So,
what went wrong with the ASC chip? Is there any possible defect that ASC internally has? Or am I going with wroing logical direction to make this conclusion?

jmg

Insufficient information - but in such situations 'divide and conquer' is usually the best approach.
ie always have more than one means of verifying an item is working.

Mike Green

Please do not start a new thread on essentially the same topic as another thread of yours. It's against forum policy and it confuses forum members. As I stated in your other thread, there's nothing "wrong" with the ASC except that it doesn't do what you want. The ASC has resistors in series with the Propeller I/O pins that are used as equivalents to Arduino I/O pins. These are necessary to protect the Propeller I/O pins from Arduino shield voltages in excess of the 3.3V allowed by the Propeller. In most cases, these don't interfere with their use as Arduino-equivalent I/O pins. When there are external pullups, as in your case, these resistors form a voltage divider with the pullup that prevents the voltage from getting close enough to zero to register as a logic zero. For that reason, the ASC has jumpers that allow these resistors to be shorted out (when the I/O voltage is restricted to 3.3V or less).

These 3.3K series resistors are recommended any time a Propeller is used with input signals that may exceed 3.3V and are recommended in some cases with Propeller I/O pins used as outputs (like servo motor signal lines). Similar resistors are built-in to the Propeller Activity Board and the Propeller Board of Education in the connections to the servo headers, so this is not a new idea.

Duane Degn

Mike Green wrote: »

Please do not start a new thread on essentially the same topic as another thread of yours.

You missed one. There are now three threads on this topic.

All the help offered in the previous threads is now unseen and people don't realize what fixes have already been suggested.

hylee101001

Thanks for the notice. I will be careful. Regarding the ASC's jumpers, are they the small holes next to the pins? I tried that but it didn't work. If those are the right ones, let me double check.

Publison

If you are talking about bypassing the 2.2K resistors, There are pads on the back of the board to do that. Just put a glob of solder or solder a short piece of wire across them.

Reference:

http://mghdesigns.com/wiki/asc:start

hylee101001

Thanks! Nothing's wrong with ASC. Something was wrong with me! Bypassing the resistrors works!