Serial to USB cable - varying results

[mackrackit]

The converters I find most reliable are
U209-000-R from Tripp Lite. They seem to be pretty close to RS232.
Belkins are not reliable, does not have the voltage swing needed by some things.

[BrianT]

Bootloaders seem very time sensitive to the variable delays when using USB to RS232 converters. Colleagues and I have tried at least half a dozen different looking adapters with netbooks, laptops notebooks and desk PCs. NONE gave 100% reliable results. Some mostly work, some never work. They are all Chinese and are generally fine for dumb ASCII communications but whenever accurate timing between sending a character and getting a reply is needed then it's back to an old PC with dedicated RS-232 DB9 connectors.

It was my design practice to always fit an RS-232/TTL port to every design and use the MCSP bootloader for field bugfixes. I have abandoned that now and use the MeLabs U2 USB programmer for all code programming and updates. I have requested Mecanique to have a look at relaxing the timing on the MCSP bootloader but that message sank without trace.

HTH
Brian

[Dave]

brid0030, I only use the products from FTDI and have had no issues using them with bootloaders or normal programming serial communications. We deal with lot's of different inferfaces here at work and the FTDI seems to be one of the best I have found. The bootloading seems to be a bit slower but never fails....

Dave Purola,
N8NTA

[Charles Linquis]

MCLoader does have some issues - especially with USB-serial. I made it work much better by disassembling it, adding a 16 bit delay after the 1st jump vector and before the loader actually started executing and then re-assembling it. I now have something that works all the time. I use only a two-wire connection (I don't control MCLR). It still loads slowly, but at least it always gets started when I turn power on.

[brid0030]

Well, I'm not attempting bootloading, just serin and serout. I'm just gonna buy a few cables and see what works. The option I will put forth to users first is to get a PC card with a com port....or just dust off that old laptop from 6 years ago.

[Charles Linquis]

As long as you are not attempting to bootload, then I think you will have no trouble. I have at least 4 brands of serial-USB adaptors, and all work fine. After you install, you may have to open up Windows Device Manager and go into the driver/properties tab in order to change the com port assigned to the device. I had one that installed itself as Com 12!

[brid0030]

Hey Charles. Thanks, but I don't think it is that simple. I have a 'no name' serial to USB cable that works with other devices, but not with the PIC/MAX232 setup. One of my collaborators reported that there was no readable communication using a radio shack cable and a compaq presario, but she got it to work with the same cable and a newer vista computer. So I don't think all cables and computers are created equal when it comes to serial to usb. I'll post what I learn when I get cables in the mail.