I have an FT232R on a 3.3V board shared with a PIC microcontroller and a MAX3232 to handle the RS232 function for the latter.
Since I don't have 5V on the board I use the USB/5V from the associated laptop to power the FT232R as in their datasheet.
All this works fine. Except---when I power down the 3.3V board/PIC/UART, the PIC remains in a sort of 2V "half state".
The FT232R is, or course, still connected to the 5V supply of the laptop. This 5V is confined only to the power pins of the FT232R and in no way ported, directly, to the board.
Subsequent investigation shows that the FT232R continues to send 16ms "wake up" pulses to the MAX3232. This is in turn carried to the PIC resulting in incomplete shutdown.
Apparently there is no 'DISABLE" or equivalent for the FT232R. Its #RESET and PWRDN pins are not for that purpose. Obviously I can complicate things, use a coveted PIC pin to control the FT232R, add FET circuits to disconnect the comms pins, and add source code to the PIC--all for lack of a DISABLE function.
But my question is-
1) Does anyone have a similar experience
2) Is there some work around I missed? Programming the FT232R (yuk!)---or some better part for this?
I thought this was a simple task!
thanks all
Fritz
Since I don't have 5V on the board I use the USB/5V from the associated laptop to power the FT232R as in their datasheet.
All this works fine. Except---when I power down the 3.3V board/PIC/UART, the PIC remains in a sort of 2V "half state".
The FT232R is, or course, still connected to the 5V supply of the laptop. This 5V is confined only to the power pins of the FT232R and in no way ported, directly, to the board.
Subsequent investigation shows that the FT232R continues to send 16ms "wake up" pulses to the MAX3232. This is in turn carried to the PIC resulting in incomplete shutdown.
Apparently there is no 'DISABLE" or equivalent for the FT232R. Its #RESET and PWRDN pins are not for that purpose. Obviously I can complicate things, use a coveted PIC pin to control the FT232R, add FET circuits to disconnect the comms pins, and add source code to the PIC--all for lack of a DISABLE function.
But my question is-
1) Does anyone have a similar experience
2) Is there some work around I missed? Programming the FT232R (yuk!)---or some better part for this?
I thought this was a simple task!
thanks all
Fritz