Usb to null modem cable drivers

The chip blew up when I move it directly to the USB port and the higher than expected voltage closer to 5V blew up the chip. If only they actually used a zener and diode. Not to say that the tolerances and proper loading of the zener diode would be done properly either. That being said, a pass transistor can be had for 3 cents, and a real requlator for a dime so yeah, you should probably use better regulation in a real design.

Well the thing died after becoming so hot the plastic case started to droop. I did it because I had a specific application where I needed serial. Ahh, the joys of asynchronous serial communications. So many ways for it not to work. I used to have a box full of null modem adapters for different applications, plus some that had pin breakouts for custom wirings.

No support for Mac OS, no support for Linux, etc. Something I never had to deal with. Reminds me of the time I tried to decipher the one-wire serial signal of Sony Ericsson walkman phones that were used for complex add-on devices, from about 15 to 20 years ago. Flow control should be implicit too.

There is something to be said for the potential to moot baud rate and word format issues. You could use two chips that implement the CDC protocol that ignores the baud rate set on the USB side, but use a standard and very high baud rate over the isolation barrier. That would mean using a microcontroller and a software implementation of CDC. Very doable, but just buying the Cypress Semi chips is vastly more convenient.

We had side-by side machines on each network with something like this in between as the only link. The files moved over the serial link via an old-school serial file transfer program running on each machine.

And, indeed, there are still Linux and FreeBSD drivers that can be used with those chips to make point-to-point network interfaces. I went with CDC for this use because I specifically needed them to be serial ports for my application. So yeah, good idea. I would be tempted to have the two sides connect via ethernet so files can be transferred faster. Also appreciate the comments around isolation.

Probably better than my strategy of just using an old cheap laptop :. Worst case you can do a bit of piping and use cat. Worked as advertised, but 1 gig of data moves really slow over USB 1. Not many people had home networks then, and wifi was pretty exotic and still as slow as USB, so I thought I was pretty slick. But I would have thought the shield on the USB cable would have balanced that before the internal pins connected, no?

Reading between the lines, it sounds like you used TP Ethernet. The magnetics that are on each end of the TP line offer galvanic isolation, so you were good.

Not sure what you mean. It was a diy ethernet crossover cable. Twisted Pair. Got it. The ground potential question was only referring to the USB cable. The ADUM provides 2. Both parts provide 12 Mbps of data throughput per direction.

I am going to experiment with a similar chip to replace the optoisolators. You may have missed the comment where I pointed out that in my particular application I must use CDC instead of double-bulk-pipe style devices. Very cool. In which case, a single cable between the two computers would give the same result. In this particular case, the manufacturer recommended two USB serial dongles with an RS null modem, but I came up with a consolidated design. I posted that on Twitter and to my surprise there was a lot of interest.

If isolation is what we need, I believe a pair of USB to Ethernet adaptors can achieve the same thing at much higher speeds, since Ethernet endpoints are magnetically coupled. Upon reading your reply to other comments, I realise that your requirements are quite different. Anyways great project!

Despite the alternatives, it definitely makes senses why one would need an isolated serial null modern. I designed one similar about 7 years ago and it is currently still sold and used by the company I worked for. Not a new concept. Yes, mine is optoisolated as well. What about this? Just have one person sit in a room looking at a screen displaying the data from the first system to be transferred in hex.

That person uses a flashlight to blink out the data using morse code. There is another person in another room watching for the light flashes that enters the data into the second system using voice to text. Oh, wait, you said this was a thing you did to solve a specific problem with a work thing that you just shared because it was interesting. And, gosh you guys, all the other comments related to floating grounds and live laptop chassis were all very scary to read.

I had no idea that all electronics are so poorly designed that even looking at them funny will let the smoke out AND electrocute me. I will never, never, never again look at two electronic things funny at the same time. Laptops as mentioned are only grounded on the AC side of the supply, not on the SELV side , you only need to look at the headphone type Jack to see the continuity to earth ground is lost.

Grab your old school VOM lol aka multimeter. Such a gadget has been available by His store has sales from time to time. Device exists! Please be kind and respectful to help make the comments section excellent. Comment Policy. This site uses Akismet to reduce spam. Learn how your comment data is processed. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies.

Learn more. Report comment. The two ground planes end at the columns of isolator pins. There is no copper between. So, from that perspective, your comment is somewhat uninformed, not to mention downright rude. That is just cruel. Other use cases might be connecting DOSBox and other emulators via null-modem connection. And if designed correctly, it will fail undervolt in case of of excess current draw. Since the signal is converted to actual uart protocol, the baud rates do need to match.

What he said. If you are connecting to a phone where the pincode has already been entered, there is no need for this. Replace 'device' with the correct USB port of your modem. You can also look for this information apn, username and password in the mobile-broadband-provider-info database from the Gnome project.

If logread shows that the connection was established and CHAP authentication was successful, but the connection was immediately dropped after, then try:. If your provider supports PAP authentication only then you need to disable all other protocols via these added options:.

If your modem needs a special AT command, your can add it to this file. This tool will report signal strength, but also network registration and SIM status. If it returns a port-in-use error because your connection is already up, try.

A higher RSSI value represents a stronger signal - scale is from 0 to 99, where 1 is the lowest detectable signal and 31 a very good signal. Don't expect your signal to go all the way up to 99, though. If BER returns 99 it means not known or not detectable. If your 3G modem is e. This is owed to the circumstance, that the device may switch over to another cell. It seems however that, in the case of 3G connections, the start scripts are started just a bit too early and the start of aiccu fails.

I have butchered the script a bit:. Note that sixxs really frowns upon quick re-re-restarts of aiccu, it may get your account blocked for unjust use of resources. Be careful with these scripts. Prepare for the next steps:We assume you have at least one 3g dongle configured. You will need an active internet connection in order to install modules for 3g support. Check 3gdongle for more information. You need to assure, that the power supply will deliver sufficent power for all of your 3g dongles.

Be generous and pick USB hub with some power source overhead. Exeplum gratum: A Huawei E has three ports. The first in is a communication port and last is a service port. A Huawei E has five ports, but similar to other Huawei devices, the communication port is the first one. Note: It seems multiwan isn't perfectly suited for 3G modems in terms of stability.

Modems don't reconnect automatically by HealthMonitor. Also, after a manual modem restart, multiwan doesn't use the newly reattached interface until it's restarted.

I had issues with auto reconnecting modems so I've modified script for checking if modems are up. This script checks modems separately. This will ping through two wans: 3g-wan and 3g-wan2 and restarts the interface in case of no replies. Additionally, It will wait 5 seconds and force a multiwan restart as it seems wouldn't recognize the new wan interfaces. Restart of multiwan should take care of this situation.

Luci has supported 3G configuration. Be sure to have luci and luci-proto-3g installed. If you want to do multiwan configuration, make sure that luci-apps-multiwan is installed and optionally, luci-app-mwan3. To create a new 3g connection, go to Luci web interface. Click on Add new interface button. You may use the following chatscript for PDPv4v6 configuration. Make sure that your dongle supports PDv4v6 2 before attempting to modify the chatscript.

See IPv6 for more explanation.