FTDI chip on propplug 5v tolerant?

Oldbitcollector (Jeff)

I'm working on a companion chip project which uses a 5v IC.
I'd like to tap the Propeller plug RX/TX lines to program it instead of
having a separate interface. Is that chip on the Propplug tolerant of
a 5v connection?

I'll share more details about this if I can make it work.

OBC

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hippy

It's an FTDI FT232RQ and looking at the datasheet it didn't appear they are explicitly 5V tolerant at 3V3; absolute max rating on I/O Vin, -0.5V to VCC+0.5V but I couldn't see any Vin max for VCCIO =3V3.

I'd expect it to work with the right R but my PropClip is too important to risk trying it on. If it's anything like the Propeller you can get away with a huge R and very little current which makes one feel a lot safer ( I use 470K for 12V on the Prop, 26uA ).

Oldbitcollector (Jeff)

Good thought, I'll incorporate some resistance into the experiment.
The companion chip is a PICAXE. I'm using it for some easy ADC and
don't really want to go through the hassle of a 9pin port, and USB-to-serial
adapter if I can just tap the pins of the Propplug for RX/TX and GND.

I'm in writing mode this afternoon, but it's slated for a test later today.

OBC

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New to the Propeller?

Getting started with a Propeller Protoboard?
Check out: Introduction to the Proboard & Propeller Cookbook 1.4
Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
Got an SD card connected? - PropDOS

hippy

You could also run the PICAXE at 3V3, run the serial through one or more diodes to drop the signal or even use a voltage divider.

Don't forget you'll need SEROUT Txxxx baud rate. If using SERTXD or wanting to use the PropPlug for download its signal polarities are inverted. FTDI's MPROG.EXE should allow that to be reconfigured.

Phil Pilgrim (PhiPi)

OBC,

The FT232R won't be 5V-tolerant when its VCCIO is 3.3V. Driving it this way risks harm to its internal 3.3V regulator. In my FT232R circuits whose targets need to operate at multiple voltages, I buffer RxD and TxD with a 74LVC2G07 powered from 3.3V. The side feeding the FTDI's RxD pin is pulled up to 3.3V. The side feeding the target system is pulled up to whatever the target system's Vdd is. The 'LVC chip is small and inexpensive: in other words, cheap insurance. I highly recommend it.

-Phil

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