Subject:
Re: DIY USB programmer ?
From:
Byron A Jeff ####@####.####
Date:
5 Jan 2005 21:39:12 +0000
Message-Id: <20050105213856.GB25012@cleon.cc.gatech.edu>
On Wed, Jan 05, 2005 at 09:10:19PM +0100, ####@####.#### wrote:
> > On Wed, Jan 05, 2005 at 05:29:31PM +0100, ####@####.#### wrote:
> >
> [Snippage...]
> >
> > I don't think speed is an issue. For the project the OP proposed, you'll
> > only
> > burn once. So it doesn't matter if it takes a minute or two.
> >
> > My concern is the cost and availablity of the parts to pull it off. FTDI
> > parts
> > are not cheap, not easily available, and are not easily usable from a
> > prototyping/breadboarding perspective. So I tabled them because that's
> > zero
> > for three.
> >
> The only big reason that ftdi chips are cheap is there relative low cost
> (as off the shelf usb chip) and the fact, that you have the possibility to
> got
> free usb identifier for a project. Not for the single individual, but for a
> company or a hobbistic group / institution. As example if the gnupic
> mailinglinst
> decide to make a usb pic programmer, then with high probability, there
> receive
> one or eight free vdi descriptors. With pic MCU's, it's not so easy making a
> legal usb device without paying fees for the usb descriptors.
I say again, FTDI chips are NOT cheap or accessible in terms of this type
of project.
To me as a developer USB buys me nothing but headaches. I would prefer
to stick to a bog standard parallel/serial port.
But as the OP has pointed out USB is going to be the interface standard
in the coming years. While USB enabled micros are coming online you'll have
the catch 22 originally described: how do you program a USB part when you
don't have a USB programmer.
FTDI is a partial solution. But while the raw chips are in somewhat the right
price range, it'll take quite a bit of work to get them going.
A USB to serial cable however is a winner. It's cheap. It plugs and works
without any additional drivers. It converts to a well know standard
interface. They are readily available. And did I mention that they were
cheap?
>
> [More snippage.]
> >
> > I know. that's why I proposed not using the modem control signals at all.
> >
> > There are no guarantees on how to manipulate the modem control signals.
> > There
> > are also no guarantees of the latency or the relationship between the
> > signals.
> The guarantees should be true, but only between rs232 frames. I have tested
> this several times on different low cost usb converters (9 - 20 Euro), but
> it's certainly
> product dependent.
So if you set a modem control line during an idle transmit, then transmit,
then you are certain that the modem control line will change before the
character is transmitted?
> >
> > Flat out I don't trust them.
>
> One note to the ftdi chip.
> This has a bitbang mode, and this mode requires a dedicated driver
> (linux/windows).
> Using this driver, a program can program 8 lines as a 8 bit port in a
> resolution of
> 2ms or 1ms, if buffering is used.
> The pins are latched every x ms (programmable) and the output/input are
> latched always at the same time. It's possible, that the ftdi chip requires
> a eeprom in
> order to enter in this mode, i don't remember if this works without eeprom.
FTDI isn't on my radar. Every time I look for ready made solutions using
them I see prices in the $25 USD range. USB to serial cables are under $10
USD now.
>
> > [Snippage ]
> >
> >
> > I think you have a skewed vision of the purpose of the project. From my
> > reading from the OP this is a single use standalone programmer for a
> > flight simulator console. It's not an ICSP programmer for general use.
> > It's a one shot one off programmer.
> Yes, i have proposed tree other low cost possibility, two of them under 10$
> including worldwide shipping.
I went back in the archives and looked at your JTAG solution.
Same question as the bitbang above: does a USB to parallel cable give you the
same access to the data, status, and control pins as you get with a bog
standard parallel port. If so then that's even a better win than the
USB to serial. I found this one at Provantage for $12:
http://www.provantage.com/buy-7mcrh00t-usb-parallel-cable-micro-innovations-hubs-switches-adapters-usb545c-shopping.htm
>
> > So it doesn't matter how RX and TX are connected. Jumpers and the like are
> > not relavent. Neither is the voltage doubler, a 9V battery as you propose
> > should be fine for a one off. Reason being is that you can use the one off
> > programmer to dump a bootloader into the chip, then you don't need a
> > programmer
> > anymore.
> >
> > The goals are to keep it dumb, simple, and cheap with easily available
> > parts.
> > And nothing is dumber, simpler, cheaper, or more available than a 555
> > timer,
> > along with a handful of resistors, transistors, caps, and diodes.
>
> But you need a non usb interface.
No I don't. That's whole point. I need a $9 USB to serial cable that's
available everywhere with drivers that are in everything. Cheap, available,
and simple.
>
> Theoreof, i can sell a 17/25(zif)$ usb programmer with shipping included,
> and a 3$ (+shipping) ICP programmer having 2K user memory expandable with
> i2c memory.
But the OP didn't really want a PIC programmer. He wanted a PIC hex file
dumper. Now if he can give his customers a hex file dumper that uses a
standard USB serial cable, a handful of parts, and some software, and tells
the user he can keep the cable after the dump, the user will be happier
than spending $28 for a PIC programmer that he'll likely not use again and
then having to wait for days and days for the priviledge.
The project isn't programming PICs. the project is building a flight
simulator cockpit.
>
> There is no real market for this type of gadged (unless you convinced me).
I have dozens and dozens of folks who have used my trivial PIC
programmer, whose purpose is similar to the OP goals: something simple
and cheap to dump code into a PIC. So there is certainly a need.
He wasn't trying to create a market. He wasn't targeting the group who
would simply buy the simulator cockpit fully assembled. His target audience
is a DIY who spend an hour wiring some cheap parts to dump code into a PIC
instead of spending $100 on a ICD2 to do the job.
USB/serial cable, handful of radio shack parts, some downloaded software,
and an hour's worth of time.
There is certainly a market for that.
BAJ
