View Full Version : Clocking the Prop off of FTDI's CBUS?
01-07-2009, 02:20 AM
I just noticed that you can configure one of the FTDI FT232R pins to give a 6 MHz clock...· I'm thinking of using that as a clock input to the Prop.· Anybody tried this before?
Phil Pilgrim (PhiPi)
01-07-2009, 03:10 AM
I think it's been done. But the FT232R uses an internal oscillator and not a crystal. So you're not likely to get an accurate enough frequency to do things like NTSC video, especially if you want color.
01-07-2009, 03:11 AM
Yep just about to try it on the next revision of the patchbox. I'm not sure it will be good enough for video generation but am going to give it a go. Just in case it doesn't work out plan B is ye olde standard crystal.
Now what I really would like to see, is FTDI incorporate an i2c eeprom emulator, so we could put a small SD card boot loader in its 1k of EEPROM.
I'll know in a couple of weeks how it goes and let you know
Phil Pilgrim (PhiPi)
01-07-2009, 03:23 AM
I found where this was done: the DLP-Prop (http://www.dlpdesign.com/dlp-prop-dsv11.pdf). Here (http://forums.parallax.com/showthread.php?p=586262) is a thread that discusses the difficulties in getting good video output from it, due to inaccuracies/instabilities in the 6MHz clock.
01-07-2009, 03:49 AM
Also, if not plugged into USB, you loose the clock, if the FTDI chip is USB powered. You have the option of powering the FTDI chip from the USB, or it can be connected to the same power supply as the Propeller.
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01-07-2009, 03:57 AM
Thanks! The DLP-Prop shows that it is possible to work...
01-07-2009, 06:46 AM
I have a dlp-prop, it is pants compared to a Prop and crystal setup.
you only get ~6MHz once it has enumerated And it is not possible to get a stable tv signal with it.
It was the first Propeller based product I bought and it almost put me off completely it was that unstable
I ended up disabling the clock outut and soldering on a small crystal, was tricky and took some effort but the difference was well worth it.
I suppose if your app isn't timing critical like tv is it will be ok though http://forums.parallax.com/images/smilies/smile.gif
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01-07-2009, 07:42 AM
Oh, I didn't know you didn't get the clock until enumeration... That's a non-starter then... I want to be able to use the mini-usb cable to supply wall power 5V...