Adafruit USB to 12v serial cable
I haven't ordered yet but us$ 12.50 for USB to 12v seriaL cable looks like a dream come true. Besides my mini I have several old devices like a old garmin etrex gps that need a real serial cable. I'm not affiliated with Adafruit, this is just the first reasonably priced adapter/cable I've found.
Source of USB to 12v serial cables
Started by Troll feeder, May 18 2011 05:15 PM
3 replies to this topic
#1
Posted 18 May 2011 - 05:15 PM
#2
Posted 28 June 2011 - 06:34 AM
Hi guys
First off, thanks Troll Feeder for this link. Unfortunately I'm not in the US so it will be much more difficult to order one.
What I would like to confirm (specifically for the Netduino Mini) is that this 12 vpp USB to Serial is the only type of converter that can actually connect to the Mini. I have found a couple of converters that say they are USB to Serial, but without enough technical info if they are 5v or 12v. Am I wasting my money buying a 5v converter if I want to use it to reflash my mini? I have a USB to TTL converter for regular programming but in the past I managed to solve a lot of issues by being able to reflash my regular Netduino (using Samba). I want to be able to do the same with my Mini.
Cheers
Pieter
#3
Posted 28 June 2011 - 06:58 AM
Hi Pieter,
The Keyspan USB-RS232 adapter should work well for you too. It may be easier to buy in your country.
To reflash your Netduino Mini, you'll need an RS232 level serial connection.
Just FYI...
3.3V TTL = [0.0V low, 3.3V high]
5.0V TTL = [0.0V low, 5.0V high]
RS232 = [-12.0V low, 12.0V high]
As you can see, RS232 has a very wide range and uses negative voltage for low signals. While the pulse patterns are identical between TTL and RS232, the voltages are very very different. [Also, RS232 can go up to -15V/15V or as low as -5V/5V -- depending on how compliant your circuit is. The Netduino Mini can handle the full range, but needs -5V to indicate low.]
Chris
#4
Posted 28 June 2011 - 09:05 AM
Thanks Chris - excellent explanation.
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