Thread: usb to parallel converters

Any idea what sort of interrupt issues laptops have? I use my usb to rs232 parallel adapter using putty or minicom terminal emulation for years and haven't had issues with throughput. Once the correct baud rate has been set. I can use these on other embedded devices similar to the arduino etc also.

Am I miss interpreting this possibly? Lol

Originally Posted by delbs

Any idea what sort of interrupt issues laptops have? I use my usb to rs232 parallel adapter using putty or minicom terminal emulation for years and haven't had issues with throughput. Once the correct baud rate has been set. I can use these on other embedded devices similar to the arduino etc also.

Am I miss interpreting this possibly? Lol

I dont know what interupts or even if my information is from this century. From experience I have seen early notebooks that struggled to even run Windows 95 so I can imagine they would struggle to do anything on time.

At the local monthly computer market there is a guy selling usb to rs232 cables and usb to centronics. Like you I bought the sr232 cable and use it on an Ardrino board and a Picaxe board. After reading your comment I think I will buy the centronics cable and try it. They are only about $10 at the market. The 232 cable drivers were very complicated to install and will only operate from one port.
One other thought, does Mach 3 see the port as centronics or usb?

I've got an iCore7 laptop which is a couple of years old now. I purchased a pccard (or whatever the hell they are called now) parallel port for it, which was supposedly usable, but I've not actually hooked it up to a gecko to test it. I understand a straight usb to parallel converter doesn't cut it.

I was mucking around with the linuxcnc.org live cd and trying to get a halfway reasonable score when my wife (god love her) purchased a Tinyg cnc controller from synthetos for christmas for me. The cost is $130, but with that you don't require a gecko or other controller, and you also don't need mach3. The savings were worth it for what I was trying to do. Runs off usb and its worked pretty well.
You hardly need any resources on the computer your running it with - just enough to send data down the usb port to the controller. The new GUI interface (tgFX) is very nice too.

If your going to buy one then check out the specs on it carefully and make sure it will do what you want. For example my 6040 cnc machine has 3 amp stepper motors, but the TinyG can only drive to 2.5 amps (per coil). I've been running it at about 2amps and haven't had any trouble, but I'm only routing wood at this stage. No idea if that would be a problem for aluminium routing - you'd need to ask somebody with some experience.

If you already have a gecko, or other parallel port controller I suspect you'd be better off going the pc card route.

If you want to check it out the website is here: https://www.synthetos.com
have a read of the forums too.

A usb to parallel port converter will not work. They designed for printers. The reason the parallel port is used in motion control is that it is a simple bunch of pins that can be run in real time. The converter will not carry all pins through, or work in real time, or at anywhere near the speed required.
The problems that occur with laptops sometimes (not always) is due to timing and power saving systems.

The smooth stepper is a motion controller. Mach 3 tells it where it should move and the smooth stepper works out the actual pulses for the motors. (Where as each pulse is sent over the parallel port).
USB is not ideal for this even so, and you'd be better off with the Ethernet version of the smooth stepper.

I use Linux cnc, and the Mesanet cards do hardware step generation and lots of inputs and outputs for a cheap price. Not sure what mach 3 support is like.

CNC4PC

with older laptops , the " bus " would be ran at 3.3volts compared to the 5 volts of a regular pc
now days there using the same chips in laptops as they use in PC's , so this problem hs gone away ( with the parallel port )

so with a 5 volt ttl logic any thing under 2.4 volts is off , any voltage higher than 2.4 volts is on ( the 1/2 way point )
if the max voltage out of the laptops parallel port is 3.3volts , and a single transistor junction knocks off 0.6 volts , the 2.7volts is only just high enough to switch on , a longer cable might be the braking point , having more resistance and dropping the voltage a little bit more , this leads to " gremlins " creeping in and intermittent false logic , 1 missed pixel is hard to see in a photo , but a missed step in cnc every 20 sec will soon add up

if the laptop has a " standard " pc chip in place ,it would be fine , if the chip is a "custom laptop chip " its more likely to run on a lower bus voltage so the battery lasts longer

most are pc chips now days ,i5, i7, i9 ,dualcore pentium , i think it was the pentium4 when battery tec caught up to he needs of a PC chip and they no longer ran a 3.3volt buss like celerons ( getting old now )


parallel ports can switch each wire at the speed of the " bus " , USB sends " packets " of information in bursts depending on chip usage , an interrupt signal coming back into the pc is almost instantly recognized with a parallel port , while with USB a flag is raised , and the computer will get around to looking for interrupts when its software tells it to look ,a big difference time between the 2

simplifed
i a parallel port wants to send the number 256 ,it would do so with 8 wires , in one " timing "

11111111

a usb is a serial communication and shakes hands first then transmits its data over eight " timings "
1
1
1
1
1
1
1
1
and then hand shakes off
another chip ( a shift converter )will assemble it into a 8bit binary , and then pass it to the break out board as 11111111

parallel ports direct access the the bus ( chip / ram / rom highway ) is a lot faster and more accurate

i was stuffing around writing a "dill " and the way mach3 uses the parallel port is amazing
0000000 8 pins all off = 0
0000001 pin1 on = 1
0000010 pin2 on = 2
0000011 pin 1 and 2 on at the same time = 3
0000100 pin 3 on = 4
0000101 pin 1 and 3 on = 5
0000110 pin 2 and 3 on = 6
0000111 pin 1 , 2 and 3 on = 7

the visual basic dill just to decide on what number to send to the parallel port , with 2 ports with 8 pins each ,made my head hurt
it ends up pretty easy
if you use a value for each pin
pin1 =1
pin2 = 2
pin3 = 4
pin4 = 8
pin5 = 16
pin6 = 32

so set each variable to only have those numbers or zero , if pin 1 is off it =0 , if pin 3 is off = 0
then a simple ,pin1 add pin2 add pin3 add pin4 add pin5 add pin6 , will give you the variable to post on the parallel port

Thanks for the info.
Looks like I should just keep the old computer going while it is working.
Regards

I have experience with the use of paralle ports.
My cnc machine came with parallel port connection and you cannot use a notebook of any sort,the machine goes crazy and the manufacturer says definitely not
In fact even with the desktop i had issues if the computer rebooted during a run the z axis was affected (drove 2.5 in down)
So you need a standalone parallel port worth about 18.00 CAN ,disable the buit in paralell ports and configure the standalone ,mine was pci and it works fine.
I also had trouble with another device (drawing tool) usb to serial adapter ,there you have to keep trying some work with xp some work with win7