FT232RL - Resetting when no USB cable is attached.

DavidM

HI,

I have a USB Adaptor I have made, using the FT232RL Chip, ( see attached schematic)

My circuit has a built in PROP RESET DISABLE function which works really well, avoiding the reset issues when the unit is operating normally.

However when there is NO USB cable plugged into my USB Adaptor, and I have the RESET DISABLE deactivated ( to allow propeller eprom writing) I have noticed that my 2 leds' RX & TX will FLASH every 10 seconds ( approx) , When I plug a USB cable in ( and the other end is connected to my PC) the LEDS don't flash and no resetting occurs.

Can someone explain what is happening?

It appears that the USB Chip wants to communicate with a USB Host?
Are there any settings in MPROG that can disable this "POLLING"


I have INVERTED the DTR# pin via the MPROG utility.
I have configured the 232RL to self powered.



Thanks
Dave M

Post Edited (DavidM) : 2/6/2010 8:37:40 AM GMT

Cluso99

The USB chip is being powered by the propeller TX (SO) pin. Have you ensured the prop has the TX pin disabled?

Since this comes up regularly, what about a diode from the prop board 3v3 to the usb 5v line so that at least the usb chip is getting 3v3?

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DavidM

HI Cluso99

thanks for the reply,

I can see this now, you are correct, I am not supplying power to the chip, so I cannot and should run this as self powered, mode, I have changed back to BUSS powered,

So you solution is to give the chip power at all time, then maybe the POLLING will stop?

I shall try a few things,

Thanks

Dave M

DavidM

HI Cluso99,

Ok, I stuck on a diode between 3.3v form the prop header to the 5v USB Connector, Geuss what , Your idea works!

Thanks mate,

Dave M

DavidM

Hi Again,

I am reading 2.8V going to the chip, the doc say it can run at this voltage, I just used a small 1N4004 diode, should I use a diode with less voltage drop?

I tested and there appears to be no leds flashing, My usb MPROG is set to SELF POWERED, and I can program the prop chip as normal, so its looking good!

thanks

dave M

Cluso99

I havent checked the spec but if it says it will work down to 2.8V that is fine. A shottky diode would drop less, but the 1n4004 is fine. Not sure what current, would presume <50mA so 1n4148 or 1N914 would likely also work.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)·
· Prop OS: SphinxOS·, PropDos , PropCmd··· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBlade Props: www.cluso.bluemagic.biz

DavidM

Hi Cluso99


Thanks for your Help,

This issue was bugging me for a long time, No my board works very well!


Thanks

Dave M

Ale

Cluso

If the FT chip is powered on the IO side by te same power rail as the propeller but not on the 5V USB side because the USB cable is not connected no reset problems should occur, right ?

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Visit some of my articles at Propeller Wiki:
MATH on the propeller propeller.wikispaces.com/MATH
pPropQL: propeller.wikispaces.com/pPropQL
pPropQL020: propeller.wikispaces.com/pPropQL020
OMU for the pPropQL/020 propeller.wikispaces.com/OMU

Cluso99

Ale: Correct

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)·
· Prop OS: SphinxOS·, PropDos , PropCmd··· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBlade Props: www.cluso.bluemagic.biz

Ale

thanks!

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Visit some of my articles at Propeller Wiki:
MATH on the propeller propeller.wikispaces.com/MATH
pPropQL: propeller.wikispaces.com/pPropQL
pPropQL020: propeller.wikispaces.com/pPropQL020
OMU for the pPropQL/020 propeller.wikispaces.com/OMU