Adding Bluetooth to Vex

[Joe Johnson]

Originally Posted by AJBelayer

... As I understand it i connect the Tx and Rx to the Tx and RX on the vex controller but then where do I connect the pwr and ground? An independent power source or is there 3V-6V power on the vex. Also I still have to check with the manufacter to make sure this is putting out TTL signal and not RS232 correct?

As to the TTL question, this is from the datasheet

Note: All pins are VDD tolerant. This means that the BlueSMiRF can interface to 5V logic, 3.3V logic, and even 6.82V logic. Onboard MOSFETs translate the onboard 3.3V to whatever voltage you power the unit to. If you power the unit with 5V, the unit will output 5V for a logic high, OV for a logic low, and can tolerate logic high levels into the input pins up to +5V.

As to the power question, I suppose you can steal power and ground from a PWM output. I have not put a meter to the power but I think it just passes power from the battery. Now that I think about it this may cause you problems.

The problem is that the Vex battery fully charged could be as high as 8V or so. From the datasheet, the input voltage would be okay (under 10V is the spec I see) but the problem is that :

1. On data TO the radio: I am not sure that the Vex TTL logic level 1 output would be read as a 1 by the radio input (read above)
2. On data FROM the radio: I am not 100% sure that the Vex TTL logic level input will like have 8V as an input

I would GUESS that it is okay, but I wouldn't want to bet my Vex controller on it.

I recommend buying a 7805 5V regulator and knocking the PWM power output down to 5V.

Good Luck.

Joe J.