Forums

USB to RS232 adapter for Flash ISP Ultility downloads?

Started by Joerg Schulze-Clewing December 7, 2005
Hello,

Downloading to boards such as Keil's MCB2103 via the Philips flash
utility requires an RS232 port. However, most new laptops don't have
one these days.

In a post a while ago I read that one of the forum members (Varuzhan)
did this but it wasn't with the newer LPC2103. So, is it likely that
any USB-RS232 adapter could work or do I have to get a particular version?

I am asking because this is a tough issue with other uC. For example,
the JTAG interface for the MSP430 won't work with RS232-Parallel
adapters even though some adapter vendors claim 100% compatibility.

Regards, Joerg

http://www.analogconsultants.com/



An Engineer's Guide to the LPC2100 Series

Joerg Schulze-Clewing wrote:
> Hello,
>
> Downloading to boards such as Keil's MCB2103 via the Philips flash
> utility requires an RS232 port. However, most new laptops don't have
> one these days.
>
> In a post a while ago I read that one of the forum members (Varuzhan)
> did this but it wasn't with the newer LPC2103. So, is it likely that
> any USB-RS232 adapter could work or do I have to get a particular version?
>
> I am asking because this is a tough issue with other uC. For example,
> the JTAG interface for the MSP430 won't work with RS232-Parallel
> adapters even though some adapter vendors claim 100% compatibility.

Hi Joerg,

I've used several USB-RS232 adapters. Both have the Prolific PL2303
chipset in them. The adapters are about $10 each.

I purchased several from TigerDirect.com.

One was a Belkin, the other was a Sabrent.

I just went to TigerDirect and searched for 'USB RS232';

http://www.tigerdirect.com/applications/SearchTools/search.asp?keywords=USB+RS232&image1.x=0&image1.y=0

The Sabrent is the second item - $12.99.

The adapter works fine with LPC boards under Windows XP and
Linux (2.6 kernels).

Cheers
Dave



Joerg,

any USB-RS232 adapter will work, downloading only uses a standard UART
protocol (115200 baud, 8 bits, no parity, 1 stop bit, no handshake). I
have used two different USB-Serial adapters myself - no brand or product
name detected on both of them ...

Some development board may use the modem control signals to reset the
lpc and ty P0.14 low. The serial cable should support modem signals for
this.

Only problem I have is that sending full speed 115200 baud serial data
from LPC to my laptop may crash the driver of the USB cable.
Most likely a reinstall of my driver will be the solution for this.

Indeed, parallel port USB adapters won't work. The wiggler software
needs direct access to I/O pins for this.
I tried something using the FT245 from FTDI but this results in very
slow communications - the FT245 can bit-bang on high speed if only
output or input is needed but when you have some input and some output
signals you'll have to wait for the next USB packet to be sent (1 ms
interval).

I am still working on my LPC2138/Ethernet based debugger pod - it should
support RDI so that it can be used with gdb/insight and commercial tools
like SDT/RealView.
(Are there still laptop without Ethernet interface ???)
Still having problems with single step/run though ... (need more input
on the way TAP works and the exact connections to the E-ICE module).

Regards,

Rob

Joerg Schulze-Clewing wrote:

> Hello,
>
> Downloading to boards such as Keil's MCB2103 via the Philips flash
> utility requires an RS232 port. However, most new laptops don't have
> one these days.
>
> In a post a while ago I read that one of the forum members (Varuzhan)
> did this but it wasn't with the newer LPC2103. So, is it likely that
> any USB-RS232 adapter could work or do I have to get a particular version?
>
> I am asking because this is a tough issue with other uC. For example,
> the JTAG interface for the MSP430 won't work with RS232-Parallel
> adapters even though some adapter vendors claim 100% compatibility.
>
> Regards, Joerg


Hello David,

Thanks. That gives me hope. I may have to order it as you did since
even the local computer stores do not carry USB-RS232 adapters of any
kind. Which I find a bit strange. Well, maybe too many people have
thrown away their old serial stuff by now.

I was hoping that at least Radio Shack would have one but I pulled a
blank on their web site. I think that the places that sell kits like
the Keil eval board should offer those converters so the
RS232-deprived could simply add it to the order. Kind of like how a
gas station will also sell snacks.

Regards, Joerg

http://www.analogconsultants.com/


Hello Rob,

> any USB-RS232 adapter will work, downloading only uses a standard UART
> protocol (115200 baud, 8 bits, no parity, 1 stop bit, no handshake). I
> have used two different USB-Serial adapters myself - no brand or
product
> name detected on both of them ...
>

Thanks for the info. Guess I have to get an adapter then. At least the
newer ones should be able to do 115200 baud.

Regards, Joerg

http://www.analogconsultants.com/



Hi Joerg,

The USB to RS232 or Parallel port converters don't retain any timing data.

The Phillips flash utility uses a standard serial RS232 interface so it
will work.

The MSP is using the serial interface but is probably using the control
signals for non serial control. If there is any timing required, it may
be lost by the USB to serial converter.

This is similar for programs that use the parallel port to control
stepper motor drivers. The generated pulse streams are time critical.
The USB-parallel converters don't give a stuff about the timing issue,
and so the timing data is lost.

Cheers,

Peter.

Cheers,

Joerg Schulze-Clewing wrote:
> Hello,
>
> Downloading to boards such as Keil's MCB2103 via the Philips flash
> utility requires an RS232 port. However, most new laptops don't have
> one these days.
>
> In a post a while ago I read that one of the forum members (Varuzhan)
> did this but it wasn't with the newer LPC2103. So, is it likely that
> any USB-RS232 adapter could work or do I have to get a particular version?
>
> I am asking because this is a tough issue with other uC. For example,
> the JTAG interface for the MSP430 won't work with RS232-Parallel
> adapters even though some adapter vendors claim 100% compatibility.
>
> Regards, Joerg
>
> http://www.analogconsultants.com/ >
>
> Yahoo! Groups Links > .
>

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Peter Homann wrote:

> The MSP is using the serial interface but is probably using the control
> signals for non serial control. If there is any timing required, it may
> be lost by the USB to serial converter.
>
> This is similar for programs that use the parallel port to control
> stepper motor drivers. The generated pulse streams are time critical.
> The USB-parallel converters don't give a stuff about the timing issue,
> and so the timing data is lost.

Another program is the USB timing. USB 1.1 has a 1 ms packet timing and
USB 2 a 128 us timing.
This means that combined reading writing (e.g. set CLK, read MISO, clr
CLK) will cost you 3 packets.
That's 3 ms on USB 1.1 and .375 ms on USB 2.

I tried using the FT245 as SPI/ISP port but stops my efforts when I
discovered this.
FT245 is great if you're only doing output (or input) you can even
specify a timing.

Rob