USBwisp

Started by July 1, 2003
I noticed that Wouter has the FTDI FT232BM chip available on his site. With his clever use of a charge pump to generate 13v from 5v in his Wisp628 programmer it seems like the Wisp628 design could be easily converted to use the FTDI chip instead of an RS232 I/F as its frontend.

Has anyone looked into this before? Wouter has a link to another USB programmer on his site but it seems to have a lot of parts but has the advantage of being able to control the VCC to the target chip.

Based on the app notes and examples on the FTDI site I threw together the attached schematic but I'm wondering if its worth it to pursue this since there are already USB to RS232 adapters out there.

dave.


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Message
>  Based on the app notes and examples on the FTDI site I threw together the attached schematic but I'm wondering if its worth it to pursue this since there are already USB to RS232 adapters out there.
 
a few remarks:
- I am working one something like this 
- this would probably be (a lot) cheaper that an adapter + Wisp628
- I am trying to make the 16F628 in the WispUSB programmable (firmware download) via the FT232
- the Vcc from USB can be too low for the Vpp charge pump, so the WispUSB must be self-powered
 

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
 




In that case, I'll leave you to your own devices. I thought that you might be since your Wisp628 design seemed to be easily adaptable into a variety of different configurations.

The addition of an eeprom to the FT232 may allow the programmer to "stand alone" with a few self-contained hex files for programming PICs in the field. But that might be for a more deluxe version...

dave. In a message dated 6/30/03 10:31:33 PM Pacific Daylight Time, w...@voti.nl writes:

- I am working one something like this




On Tue, 1 Jul 2003, Wouter van Ooijen wrote:

> > Based on the app notes and examples on the FTDI site I threw together
> the attached schematic but I'm wondering if its worth it to pursue this
> since there are already USB to RS232 adapters out there.
>
> a few remarks:
> - I am working one something like this
> - this would probably be (a lot) cheaper that an adapter + Wisp628
> - I am trying to make the 16F628 in the WispUSB programmable (firmware
> download) via the FT232
> - the Vcc from USB can be too low for the Vpp charge pump, so the
> WispUSB must be self-powered
>
Don't even think to a self powered scheme and an USB connection !
It's a sacrilege. A leack of respect for the USB creators :)))
Any supply may be used with a simple dc/ac/dc converter to give any
voltage, including the Vpp.

Vasile



> Don't even think to a self powered scheme and an USB connection !
> It's a sacrilege. A leack of respect for the USB creators :)))
> Any supply may be used with a simple dc/ac/dc converter to give any
> voltage, including the Vpp.

That might be true, but it would add a significant number of components
to the programmer. And Wisp is an in-circuit programmer, meant to be
connected to an aready working (and hence powered!) target circuit, so
my choice would still be self-powered.

For an experimentor's board (programmer/bootloader, target, some I/O to
play with) the situation would be different, for such a board it would
be very convenient if it could be plugged into USB without needing an
external power.

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products




On Tue, 1 Jul 2003, Wouter van Ooijen wrote:

> > Don't even think to a self powered scheme and an USB connection !
> > It's a sacrilege. A leack of respect for the USB creators :)))
> > Any supply may be used with a simple dc/ac/dc converter to give any
> > voltage, including the Vpp.
>
> That might be true, but it would add a significant number of components
> to the programmer. And Wisp is an in-circuit programmer, meant to be
> connected to an aready working (and hence powered!) target circuit, so
> my choice would still be self-powered.
>
> For an experimentor's board (programmer/bootloader, target, some I/O to
> play with) the situation would be different, for such a board it would
> be very convenient if it could be plugged into USB without needing an
> external power.
>
As far I know, there are printers which are powered from the USB (Up to
1..2A). Then why not the user application ? Via a current limmiter,
just for two left hand users. I'll use with pleasure the USB as the power
supply for my development board. Anyway, a fuse is always on the motherboard
both for the USB and for the keyboard.
So, let the user to choose the supply methode, from the USB or from the
target. At the end, you are doing just you like, anyway. :)

Vasile



> So, let the user to choose the supply methode, from the USB
> or from the
> target. At the end, you are doing just you like, anyway. :)

Of course I'll do what I like ;)

But the point is that having the USB line power the programmer requires
a step-up converter (because the Vpp pump will not be reliable at the
lowest voltage that an USB line might provide), so it would make a more
expensive programmer, even for the people (IMHO most users) that do not
need it.

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products



On Tue, 1 Jul 2003, Wouter van Ooijen wrote:

> > So, let the user to choose the supply methode, from the USB
> > or from the
> > target. At the end, you are doing just you like, anyway. :)
>
> Of course I'll do what I like ;)
>
> But the point is that having the USB line power the programmer requires
> a step-up converter (because the Vpp pump will not be reliable at the
> lowest voltage that an USB line might provide), so it would make a more
> expensive programmer, even for the people (IMHO most users) that do not
> need it.
>
As you say my friend. However see how much it cost an ICL7660 for
example. Or a 555. On SSOP of course, to avoid wholes... :)

best wishes,
Vasile


 As far I know, there are printers which are powered from the
USB (Up to
1..2A). Then why not the user application ? Via a current limmiter,
just for two left hand users.
from my head:
the FTDI chip without eeprom can only provide 100 mA.
With a eeprom, you can tell the PC you're connecting a high power device,
which can draw a maximum of 500 mA.
There's another important reason to use eeprom with the FTDI chips,
if you don't use it, you can have only 1 FTDI chip connected to your PC,
with eeprom it's unlimited.

Stef Mientki


d...@aol.com wrote:
I noticed that Wouter has the FTDI FT232BM chip available on his site. With his clever use of a charge pump to generate 13v from 5v in his Wisp628 programmer it seems like the Wisp628 design could be easily converted to use the FTDI chip instead of an RS232 I/F as its frontend.

Has anyone looked into this before? Wouter has a link to another USB programmer on his site but it seems to have a lot of parts but has the advantage of being able to control the VCC to the target chip.

Based on the app notes and examples on the FTDI site I threw together the attached schematic but I'm wondering if its worth it to pursue this since there are already USB to RS232 adapters out there.

dave.
about a year ago I build a number of these,
    http://oase.uci.kun.nl/~mientki/PIC/PicProg/PicProgrammer_hardware.htm
they work great (now I tend to bootloaders for all cases where I use larger PICs with almost always an USB connection).

Dontronics, and or some other firm (with very small programmers), now also has cheap USB programmers.

Stef Mientki