PICAXE usb to serial adapter help.

navelooc

New Member
hi i am attempting to utilize a USB to Serial adapter that converts into an audio jack into my training board. i am trying to get the adapter to work. i have dounloaded all drivers and confirmed that it works properly, but when i try to use it in Programming editor it says, "serial port error-port not present or already in use." tech support told me that i may have to change some numbers for that port (i think he said IRQ numbers?) but thats all he could tell me. does anyone know what i need to do to get this thing working? the adapter is an AirLink101 Model#AC-USBS and the PICAXE is the 08-M. thank you for any advise you got.
 

BCJKiwi

Senior Member
OK, we need to establish if the issue is with he USB port, the download cable, or the Picaxe board.

Which of these three can you confirm is 100% guaranteed OK?

The error message reported indicates that either some other program has linked to that port, or the Programming Editor can't find it.

Have you tried re-starting the PC after making the port changes etc. If not it's worth a try.

Do you have anything else you can test the adpter with - i.e. some other serial device? you indicate that you have confirmed it works correctly which suggests another serial device or port - if not, how did you confirm it works properly?
 
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kevrus

New Member
Just a stab in the dark, but with the download lead plugged into a usb socket, have you then tried pressing the 'refresh' button in 'programme editor - options - refresh' box as with mine, it then allow me to select another port (com 5 for me)
 

Technical

Technical Support
Staff member
"AirLink101 Model" is not a supported model of adapter. Use part AXE027 or USB010 instead.
 

BCJKiwi

Senior Member
I am a little puzzled by the apparent necessity to use Rev-Ed's version of USB-Serial Adapter.

There are a number of chipsets doing this job which work fine for everything else I've used them for. Why is the Programming Editor so dependent on one chipset?
 

eclectic

Moderator
BCJ. You know what you're doing.
People like me may not.

I've got a several assorted adapters/cables in my "recycle" draw. They didn't work.

I now own USB010, AXE025, AXE026 and AXE027.

They work.

e.
 

demonicpicaxeguy

Senior Member
if you look at what each different adapter puts out in terms of voltage levels you'll get a nice suprise, some put out the proper voltage about 10v and quite a few of them put out as low as 3.3 for a 1,

the one rev-ed uses isn't a bad one , just if you use it a great deal take some extra care not to pull it off sockets by the cord,
mine recently when i plugged it into my usb socket returned serve with a puff of smoke, when i pulled the adapter apart i found that the years of use and abuse had seen the wiring pulled from the pcb and shorted out together ,
 

BCJKiwi

Senior Member
@eclectic,
Sorry but that was not the point I was trying to make. I certainly don't claim to know what I'm doing all (or even very much of) the time. Its not a matter of what I may or may not be able to get working.

A 'standard' program should work with 'standard' chipsets.
The range of usb-serial adaptors on the market use a number of different chipsets and seem to work with many different 'standard' programs.

I have a non Rev-Ed adapter which works in three different PCs with number of different programs. (I have not tried using the Programming Editor on this adapter but have just tested it and it reads the firmware of a 28x1 at 16MHz so I guess this one would work -its a Prolific chipset PL-2303 what ever that means)

It seems that the Programming Editor is not a 'standard' program in that it does not work with any adapter but Rev-Eds.

I was just wondering why.

(Post crossed with yours Demon)
 
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papaof2

Senior Member
The incompatibility is not between the Programming Editor and the USB device.

I've been using a "generic" USB<->serial adapter sice I started using PICAXEs and the key feature of the adapter is that it uses the Prolific chipset, which presents a very accurate serial port to the PICAXE - and its driver provides a standard interface to the operating system (Win XP).

The Programming Editor expects to find a "standard" COM port interface, whether a physical 9/25 pin port or a USB<->serial adapter. If the COM port can't be found (after a refresh), the most likely problem is with the device driver for the USB<->serial device.

Also note that Win 98 often does *not* recognize USB devices that are connected after startup. If the device is there at boot, it will be found; otherwise Win 98 does not see the device (one of the limitations of USB 1.x). Win XP with a USB 1.x port may not see a device plugged in after boot (I can demonstrate this on my XP laptop with a thumb drive, among other things). USB 2.x ports are usually much better at recognizing and configuring devices that are connected after boot. Putting a USB 2.x hub on a USB 1.x port (before boot) may resolve the problem with devices not being found (works for me with thumb drives and USB hard drives) and it may also depend on the specific hardware involved.

John
 

navelooc

New Member
thank you

i finally got it to work for me, i just used a different USB port and a new COM. works fine. thank you very much for all the input, greatly appreciated.
 

hippy

Senior Member
The technical issue with some USB-to-serial not working with the Programming Editor is how that USB device and its driver handles a 'break' on the PC transmit line. This is a prolonged high signal which needs to get to the PICAXE for successful download. Because a 'break' isn't a normal ASCII character some drivers simply ignore it and don't pass it onto the PICAXE.

'Break signalling' is not uncommon ( headless servers often require it ) and has been around for years so any failure to support it is down to the USB device manufacturer or whoever wrote their driver. It's their fault their device won't work with the PICAXE / Programming Editor.
 

Technical

Technical Support
Staff member

For those interested, as Hippy says the PICAXE uses the RS232 'break' command.

The simple fact is that some cheapo USB adapters do not correctly emulate the UART hardware. They should, but for some reason they never implemented it correctly.

The better chipsets, such as Prolific (in the USB010) and FTDI (in the AXE027) do. The break feature is also used on many commercial machines - in fact the robotic programmers we use here for programming PICAXE bootstrap use it aswell!

A pretty good explanation of the UART hardware registers is here:
http://www.beyondlogic.org/serial/serial.htm

Technically set/clear 'break enable' is bit6 of the LSR register, which is located at UART base address + 3. e.g. if COM1 is set at 3F8, LSR is at 3FB. The exact same LSR register is also used to set the parity, number of bits and length of stop bit - all essential for RS232 communication at any baud rate, so it is very strange that some USB adapter manufacturers simply ignore this bit when they obviously took care of emulating the other bits in the same byte!

Any USB-serial adapter that "correctly" emulates all the serial UART behaviour will work with the PICAXE system.
 
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