Summary of Arduino USB
The article discusses creating a low-cost USB to TTL serial interface to program Arduino clones like RBBBs or Boarduinos, which lack built-in USB connectors. Commercial USB-to-TTL converters such as the USB-BUB are effective but costly. The author experimented with a cheap USB to RS232 Serial DB9 adapter cable containing a PL2303 chip, hoping to use it for programming, but found it incompatible due to RS232’s voltage levels differing from Arduino’s TTL requirements. The article highlights the challenge of converting RS232 signals to TTL logic for Arduino programming affordably.
Parts used in the USB to TTL Serial Interface Project:
- Arduino clones (RBBB, Anarduino, Boarduino)
- USB to RS232 Serial DB9 Adapter cable with PL2303 chip
- USB to TTL converter (USB-BUB by Modern Devices) - referenced for comparison
LOG: Made a correction/modification Step 3 and added a picture step 5.
So many Arduino users have RBBBs(Really Bare Bones Board (Arduino)) or Anarduinos or Boarduinos that could use a USB interface to program and power them but don’t want to spend $15-20 for a USB BUB or FTDI cable. This Lazy Old Geek is one of them.
Theory: Most Arduino clones are programmed with a PC using a USB port. Theoretically, they could be programmed with an RS232 port but it is really hard to find a PC with RS232. Some Arduino clones come with a USB converter but most do not. Most require a TTL serial connection. TTL stands for Transistor-transistor-logic which basically means 0-5Vdc logic. So these Arduinos require a USB to TTL converter. One of the more common is the USB-BUB by Modern Devices:
http://shop.moderndevice.com/products/usb-bub
I own one and like it but they’re costly.
So I saw these (see picture) USB to RS232 Serial DB9 Adapter cables on ebay for less than $2 so I bought one. Since I had three weeks to wait for it, I thought about and realized that it probably wouldn’t work as true RS232 has plus and minus 3-15 Vdc signals. The Arduino requires TTL levels which are 0 and 5 Vdc. Nevertheless, I’d already bought it so I took it apart. It apparently had a PL2303 chip in it and I saw no level converters. Anyway, I don’t have any kind of RS232 device to check it with but don’t see how it could ever work with a true RS232. But the other thing is; I couldn’t get it to work with an Arduino. If anyone has gotten one of these to work, please let me know how.
For more detail: Arduino USB
