[Hardware] Serial Adapters...GET ONE!

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[Hardware] Serial Adapters...GET ONE!

Postby xenoxaos » Tue Jul 30, 2013 1:40 pm

First things first....if you don't have a serial adapter yet...scrounge up at least $5 and get ready to buy one after this.

If you haven't bought your ARM device yet, check and see if the seller offers a serial adapter with it. Buying it now with the device can save you shipping charges later...especially if you have an ODROID.

Why should I get a serial adapter?
A serial adapter is good for any time you want to mess with u-boot settings or things just aren't coming up right. By default, many of the devices output debugging information and boot logs over serial. If you ever want to say "it powers on, but I don't get any ssh" on the forums or IRC, a serial adapter can save you so much time and frustration of getting it working again.

Hardkernel/ODROID specific adapter
Alright. If you haven't bought your ODROID yet...hold off a few minutes before checking out. Aside from being a different voltage than most of the other ARM boards (1.8v vs. 3.3v) Hardkernel has a special connector for their serial connector. It's a very robust connection and doesn't fall out easily like using jumper wires on other boards. Their serial adapter is specifically made for their ODROID boards and can't be easily used with other boards. You wouldn't want to anyway. It's $15 but if you forget to buy it with your board, just shipping the serial adapter is ~$25. So, do yourself a favor and add it to the cart. (also consider an eMMC module too. I recommend the 16GB. The transfer rates are at least double that of a SD card).

Now on to the others...

There are many other serial adapters. One thing you want to make sure about is the voltage of them. If your computer has a serial port....DO NOT USE IT! The RS232 standard specifies a maximum voltage difference of 50V! Most computers won't be that, but still...just don't use it. You will most likely need to use a USB<->serial adapter. Luckily, they're cheap and easily available world wide.

If you have a Pandaboard or something else with a DB9 connector on it, connecting a serial adapter to it is really easy. Adafruit sells a DB9 Serial Adapter in their store. Just plug it in and you're good to go!
If you need access to the other serial ports on the Pandaboard, those are 1.8V so plan accordingly with a jim.sh or similar 1.8v compatible adapter.

If you have any other board, most likely your serial port will be 3.3v...but make sure before hooking something up. There are many different serial adapters that will work with 3.3v, and they have different chips in them. In my opinion, and many others' opinions as well, the quality of the FTDI chip is better than the Prolific PL2303 chips. And their cost shows it. You're not likely to find a FTDI adapter for under $10. The following links are to reputable companies that I can vouch for their products and customer service.

FTDI based adapters:
SparkFun FTDI Basic 3.3v Breakout 3.3v
SparkFun FTDI Basic 3.3v Retail Packaging
jim.sh - This one can be both 1.8v and 3.3v, but only use if you're comfortable with a soldering iron.

PL2303 based adapters:
The following are most likely PL2303 based, but this is an assumption.
Adafruit DB9 serial
Adafruit 3.3v serial
Olimex 3.3v Female Terminations
Olimex 3.3v Male Terminations male

Now...You can find much cheaper devices on ebay. Often, you get what you pay for. The serial adapters I've gotten on ebya have been hit or miss. Some of them have worked with no issues. Some of them have caused kernel panics and blue screens. A couple of them have outputted garbled text at higher bitrates (115200) and couldn't really be used. Some of them have worked for a while then randomly stop working after a month. You have been warned. If you go the ebay route, I recommend getting several at once.
To find an adapter on ebay, just search on "pl2303 3.3v" or "usb serial ttl 3.3v" or some combination of "3.3v" and "usb ttl serial pl2303 ftdi" and you should come up with many of them.
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