Extracting a UART Password via SPI Flash Instruction Tracing
zuernerd.github.io37 points by Eduard 4 hours ago
37 points by Eduard 4 hours ago
It’s too bad Saleae prices are so high now. Their original models launched at a very affordable price point but that’s long gone.
In the past they’ve offered discounts to students and contractors if you know where to look and how to ask: https://blog.saleae.com/saleae-discounts/ If anyone is considering one, it’s worth a try to see if they still honor this.
The alternative logic analyzers mentioned in this article look interesting, but the software side leaves a lot to be desired. Some people get along okay with PulseView (or forks, like in this article) but I never enjoy using it.
Very nice!
An 8051 with XIP SPI flash - that must be ancient tech.
Not necessarily, there are 8051 soft cores you can get for your FPGA/ASIC.
do you know the SPI clock frequency? I am trying to figure out the sampling rate required to reliably capture the trace. That determines the tier of logic analyzer needed I guess.
A few ways:
1. Read the datasheets. Some parts only support certain frequencies, so find the minimum of the master and slave frequencies. 2. Check at boot. Most devices boot slowly for the first few transactions then speed up. So if you saw valid data then aliasing, get a better kit. 3. Start high. I think the fastest serial memory devices cap out at 250 MHz DDR for volatile and 200 for non-volatile. So even a digital discovery (which I think is the best LA for high speed bursts) can deal with it
in this particular case "We need to be able to capture 60 MHz SPI."
For something cheap and capable you could try building rp2350 based https://github.com/gusmanb/logicanalyzer, goes up to 400Ms/s. Its just a Pico1/2 with a level shifter board
"This is an affordable logic analyzer capable of reaching up to 400Mhz of sampling speed. The analyzer uses a Pico/Pico2 as its core. The analyzer offers 24 channels but can be chained up to 5 devices allowing the sampling of up to 120 channels at once."
I havent played with their software yet, but I have a ton of experience with pulseview and while its feature rich it is sluggish and not suited for high speed big volume acquisitions (especially the dreadfully Python 3.4 plugins and Im saying this as an author of one of the plugins) so anything written even half competently might be better.