com -> usb converter

[zoharl]

I've read somewhere that I can simply use a converter to connect the R232 of the programmer to the USB computer. Although it won't benefit the usb advantages it should work. if I don't have a com port in my pc.

Does it sound good to you?

 

[Nigel Goodwin]

Depending exactly what it's doing, they generally work well - maximum throughput is usually only 9600 baud or so though. I've actually got a Belkin one connected to this very computer.

 

[picbits]

Yup - I use a couple.

One for my programmer and one for my project (I use a bootloader on a PIC18F1320)

Never had any problems yet with them

 

[picbits]

Depending exactly what it's doing, they generally work well - maximum throughput is usually only 9600 baud or so though. I've actually got a Belkin one connected to this very computer.

Mine are quite happy at 19200 for the bootloader and 56,000 (ish) for the programmer.

 

[Nigel Goodwin]

Mine are quite happy at 19200 for the bootloader and 56,000 (ish) for the programmer.

You can connect them at 115,000, and they work fine - but the throughput is still only about 9600 baud. The reason is simple, serial is a byte at a time, USB is packets or continuous bytes, and USB isn't interrupt driven. The overhead sending a single byte via USB is huge, this absolutely cripples the speed. Presumably if you're using USB 2.0 it would be faster though?.

 

[jeremygaughan]

but which programmer?

Which programmers are you all connecting with a USB R232 converter?

 

[picbits]

I use the Picstart and Promate II as well as custom written bootloaders.

 

[blueroomelectronics]

I've used a PL2303 with my ICD2 clone.

PS picbits what are you using the PIC18F1320 for? I'm asking as it's the PIC I chose for my next kit (Junebug)

 

[picbits]

I've used a PL2303 with my ICD2 clone.

PS picbits what are you using the PIC18F1320 for? I'm asking as it's the PIC I chose for my next kit (Junebug)

I use them for just about anything that doesn't require too many I/Os

Current products are:

Frequency pulse converter for use in cars - converts speedo or tacho pulse to a multiple of the input frequenct

Addressable LED multiplexed drivers

Adjustable radiator fan control and multiple relay controller for cars

Rev counter shift lights

Basic data acquisition systems with serial output for external datalogging



For the bootloader I just adapted the Microchip bootloader for the 1320, added a couple of lines of code so that holding a pin high on powerup will enter the bootloader and edited the .ini files from Microchip so their bootloader front end will talk to the processor.

 

[Edd]

This forum is great, I've been reading for awhile and finally decided to join.

I attached a file of the converter I built a couple of years ago with parts from Futurlec (Took 6 months + to receive the stuff though). The guy's website appears to be down, but I saved a pdf of it when I built it.

I haven't gotten into programming pics, etc yet, but I made this and it worked fine on a mac with the old lego mindstorms.

 

[Sceadwian]

Nigel, most serial to USB converters will buffer data for USB transfer, and won't send it just a byte at a time, depends on the program accessing the com port and the chip in the converter though. I've seen chips rated at a megabaud for buffered transfers.

 

[Nigel Goodwin]

Nigel, most serial to USB converters will buffer data for USB transfer, and won't send it just a byte at a time, depends on the program accessing the com port and the chip in the converter though. I've seen chips rated at a megabaud for buffered transfers.

'Most'?, you mean an odd few might?, and doing so would also further limit their usefulness - like you say, even with buffering, it depends entirely on the program accessing the port, and what it's doing - other than feeding a modem, most serial port programmes would be single byte at a time.

Presumably you're talking about more modern converters?, when Elektor tested them, all the ones tested had really slow throughput, because of the single byte overhead problem.

 

[Sceadwian]

I guess I'm talking a bit one sided, as I've only really looked at FTDI chips, guess I was assuming other chips are the same, sorry. They provide a generic USB to serial dongle for basic RS232 functionality.

**broken link removed**

As a generic windows com port it goes from 300 to 230kbaud. The special direct drivers allow up to 1Mbaud for RS232 and 3Mbaud for RS485 and direct TTL, but I don't think this generic dongle has support for baud rates that high.
I can't check the Elektor results you mentioned because I won't register to every website for individual articles I'm interested in.

 

[Nigel Goodwin]

I can't check the Elektor results you mentioned because I won't register to every website for individual articles I'm interested in.

I won't either!.