MAKE: AVR Programming - Page 1
Forum section: electronics / beginners

author: aewm96
author_rank: Newbie
timestamp: September 23, 2021, 04:32:03 pm
content: Hi All,I'm buying a few items so I can work through the MAKE: AVR programming book but the one item I am unsure about is the USB to Serial Cable that is mentioned."A USB-to-serial adapter. I’m a big fan of the FTDI USB-Serial cable. Get the 3.3V-compatible one for maximum flexibility"When I've looked there are different types that talk about RS485 and other variants and I was wondering which I should get or if they are all realistically compatible? (I don't believe they are but I could be wrong!)I was thinking that this would be a suitable option:https://ie.rs-online.com/web/p/development-tool-accessories/7158522/Thanks for your help!

author: rstofer
author_rank: Super Contributor
timestamp: September 23, 2021, 04:58:19 pm
content: I have both the 3.3V and 5V versionshttps://www.amazon.com/gp/product/B00DDF8TV6https://www.amazon.com/EZSync-serial-TTL-232R-5V-WE-compatible-EZsync009/dp/B010K5NC68

author: madires
author_rank: Super Contributor
timestamp: September 23, 2021, 05:24:27 pm
content: There are tons of inexpensive CH340 based USB-to-serial adapters which have a jumper for setting either 3.3 or 5 V.

author: Ian.M
author_rank: Super Contributor
timestamp: September 23, 2021, 05:37:34 pm
content: Its also worth considering FTDI'sTTL-232RG-VIP-WEadjustable voltage cable. Instead of providing a supply voltage output, it has a wire for the FT232R's VCCIO which sets the target I/O levels so you can use it with any target Vcc from 5V down to 1.8V.Another option is to use a FTDI breakout board and make your own cable. e.g. Sparkfun'sBOB-1231FT232R breakout, which is switchable between 5V and 3.3V levels, or the ubiquitous CJMCU-232H FTDI FT232H USB <=> serial breakout board, which is cheap and widely available, but suffers the disadvantage of using fixed 3.3V output levels though all its inputs are 5V tolerant. The FT232H is not just a UART, it can also do I2C and SPI (both as master), JTAG and bit-banged GPIO. Caution: The CJMCU-232H 5V output is direct from USB Vbus and is *NOT* fused or otherwise protected, and its 3.3V regulated output is strictly low current.

author: aewm96
author_rank: Newbie
timestamp: September 23, 2021, 06:10:22 pm
content: Thank you for the fantastic advice. I like the first option of using a voltage adjustable cable which I think will be the versatile option for beginning with this book. I'll also source the FT232R board and use that for when I am far more comfortable with this stuff!Thanks for the warning because I would have 100% expected that to be protected in some fashion. Sounds like you are speaking from experience @Ian.M

author: Ian.M
author_rank: Super Contributor
timestamp: September 23, 2021, 07:25:27 pm
content: Yes, the adjustable cable is neat, and great for experimenters, provided your target has its own power source.Personally I like the CJMCU-232H board, because it does far more than simple UART serial comms, but I have nearly smoked it by a short on its 5V rail which if I had taken a few more seconds to spot, would have burnt tracks off it, and possibly blown out one of my PC's USB ports. However, that's a risk you take any time you don't use a USB isolator with a current limited Vbus supply between your USB connected experimental circuit and your PC.

author: rstofer
author_rank: Super Contributor
timestamp: September 24, 2021, 01:17:53 am
content: A USB Isolator is a great tool to have. So is a powered USB Hub between your PC and project.