USB converter cable problems

[spamiam]

I have a USB to Serial converter cable. It has an FTDI chip inside. I had thought that FTDI made reather reliabe converter chips. The cable works fine on other devices, but totally fails to work with the ZX24.

I think I need to get a different converter, such as the one for sale here. I looked at the schematic and realized that the FTDI chip can get the I/O voltage from the destination device (e.g. 5V).

But the cable has no power connection from the destination, so what voltage do these cable-type of converters (the ones that only end in a DB9 connector) use for I/O? 3.3V from the USB bus?

How important is it to have 5V on the I/O to the ZX for communication reliability?

I'd love to have the converter PCB housed in a box with a DB9 on the side, and the USB on the other side. But then I would not be able to get the 5 volts from the ZX. Is there a solution to this?

-Tony

[dkinzer]

[stevech]

timing of ATN (one of the RS232 lines, DTR) can be an issue with USB-serial.

FTDI has the best Windows drivers for USB, IMO. But there remains irregular and somewhat unpredictable timing of toggling ATN. And the PC side software that does so is often rather intolerant. I vaguely recall changes made to the PC software to lessen restrictions; check your version #.

However, I have a ZX24A that works reliably with a no-name USB adapter that uses an FTDI chip. So all of what I said above may be irrelevant to your situation!

[spamiam]

Well, I have to check my USB adapter to see what it has in the way of voltage levels.

I had assumed that it would be outputting at the full RS232 voltages, but I have no idea what it really does. 3.3 and 5.0 volts seem possible. If I had to guess, I would assume that it would be outputting voltage at the same level as the USB power supply rails.

The only thing I really tested was trying to download, and it failed so badly that ZBasic crashed. I tried a few times before I gave up.

I ordered an adapter from Mouser that has a REAL FTDI FT232RL and has user selectable 3.3 or 5 volts on the output. It is not a cable, however, it is an in-line adapter module. $23 +shipping. Here is hoping that it will work!

-Tony

[dlh]

You could have saved a bit by buying...

http://www.sparkfun.com/commerce/product_info.php?products_id=718

It comes setup for 3.3V but you can change a (soldered) jumper for 5V or other output.

[GTBecker]

I use a modified PropPlug: http://www.zbasic.net/forum/about603-0-asc-15.html and have had no difficulties with it. It has proven to be very useful so I place a four-pin SIP alongside each processor I use.


Tom

[spamiam]

I have ordered this one.
http://www.mouser.com/search/refine.aspx?Ntt=626-DLP-EVAL232R

I wil see how it works.....

-Tony

[dkinzer]

[stevech]

here's one I use with ZXs - has FTDI chip.
It's marketed under several trade names.

Has FTDI's logo in a obscure place on the retail package; that's the clue.

[spamiam]

decided today to get a usb->serial converter working if it killed me.

I had gotten a new FTDI EVAL232R adapter. This is a fully implemented FT232RL device. If ANY converter is going to work, this one should.

Previously I had a different FTDI-based converter cable which would not work properly.

I tried my EVAL232R and it totally failed to work!!! I pulled it out and tossed it onto my shelf in disgust.

I went to the FTDI website to see what I was doing wrong. The answer is either nothing or everything.

I learned about latency in one of their AppNotes (AN232B-04) which I found on this page: http://www.ftdichip.com/Documents/AppNotes.htm

I learned about changing the advanced settings in the serial port control in the System hardware manager. The default latency is 16 milliseconds. This is almost certainly too long for the OM128 bootloader. I changed it to 1mS and then tested the EVAL232R.

It STILL did not work. Not at all. But then I realized I needed to set the proper COM port. When I did that, it worked. Perfectly. Did I have the right COM port selected when it failed the first time I tired it? I am not sure. I went back and reset the port settings back to the 16mS default. The converter STILL worked fine.

I then installed the cable converter that did not really work properly, and tried it again. It again failed. I set the letency timer back to 1mS and it this one works too!

If this had not worked, or if I have glitches in the future, I will try to adjust the "USB Transfer Size" (also in the advanced section of the port settings). It defaults to a relatively large 4096K. I would set it down to the minimum of 64 bytes and see what happens there.


I am not sure if NON-FTDI converters have the same settings, but if they do, then try it.

-Tony

[DocJC]

I have been using a Keyspan USB to Serial cable converter without any difficulty, on a WinXP system. It is Model USA-19HS. I do not see a FIDI logo on the smoked black plastic case. The web site indicates that it is Windows, Mac, and Linux approved. www.Keyspan.com

JC

[spamiam]

JC,

You might be able to tell if it is an FTDI chip by looking at the driver of the USB serial port. But the manufacturer could have changed the info in the standard FTDI drivers.

Also, FTDI has an EEPROM programmer utility that would be able to tell you if the chip is an FTDI device.

http://www.ftdichip.com/Resources/Utilities.htm#MProg

-Tony