If you are starting out in hardware hacking, then you need a toolkit. For some aspects of this, it’s worth spending good money for a quality tool. For other parts, low-cost alternatives can be better.
This post details what I would consider the absolute starting point.
Your multimeter will be one of your most commonly used tools. Most of the time, you will be in continuity or voltage mode. Sometimes you will be measuring resistance. Rarely will you measure current. Frequency, capacitance, and duty cycle are virtually useless for embedded systems.
You want a responsive and loud continuity buzzer – ideally a “latching” one. This is virtually impossible to determine from specifications – YouTube reviews will often cover this.
From a usability perspective, it is desirable that the meter has a dedicated continuity mode or stays in continuity mode through power-off. Many meters require a button-press to go from resistance to continuity mode, which leads to using the meter in the wrong mode.
An auto-ranging meter generally makes work quicker, as you don’t need to change the range. Be warned though, some cheap meters have incredibly slow auto-ranging, which becomes frustrating quickly.
Separate current and voltage terminals are essential. Some meters share a single terminal for both, with the function being changed by a selector dial. This changes the meter from high-impedance (>1MOhm) to low-impedance (<1Ohm), which can lead to mistakenly shorting out power supplies.
In terms of resolution, accuracy, and precision, we generally aren’t bothered as long as the meter isn’t truly shocking. Anything with less than 4000 counts may not be adequate.
Multimeters have varying levels of safety. Unless you know the meter is a genuine one from a reputable manufacturer (Fluke, Brymen, Agilent/Keysight, Amprobe etc.), be extremely cautious using them on mains voltages or in high-current situations.
This isn’t the place to be discussing the difference between CAT II/III/IV meters, but if you are working on mains installations, I would strongly recommend following the route electricians have: two pole testers that simply cannot measure current.
My recommendation is the Brymen BM235. This is a reliable and accurate meter that does nearly everything you will need. If you think you will be in this game for the long run, I’d really recommend getting a decent meter.
The probes that come with your meter will likely have large, relatively blunt tips. In my opinion, a major upgrade is switching to needle probes.
There are very fine probes which are as sharp as a needle. They make it easy to probe individual pins on fine-pitch semiconductor packages. Because they are so sharp, they allow you to break through oxides, conformal coating, and solder masks easily.
The image below shows a 0.5mm pencil, a needle probe, and the sharpest normal multimeter probe I have. There is a very clear difference.
I recommended Pomona 6275 for this. These ones come with stainless steel tips, which are very sharp and robust, but at the cost of slightly increased contact resistance.
Be warned, this can only carry 3A at 60V. They are not suitable outside electronics.
Connecting to serial consoles is extremely common. I’m a big fan of cheaper USB-to-serial adapters based on the CP2102/4, FT232R, and PL2303. There’s very little to differentiate between them in functionality. Some support 5V and 3.3V operation, but nearly all of the time 3.3V will be what you need.
These are the kind of devices that you lose, get borrowed, or break. You can order packs of 5 from Amazon for around £10-12. However, you can also buy them for around $0.70 from Aliexpress, which works out to around 70p each with postage.
USB Ethernet adapter
You are likely going to end up working with Ethernet connected devices, and want to pass traffic through to a virtual machine. Rather than bridge to the physical adapter, I find it is far more versatile to use a USB Ethernet adapter.
I like the Amazon basics ones. They work well, the link and activity lights are exposed, and they have the MAC address printed on the back of them.
It is also worth sourcing a USB 2.0 Ethernet adapter – these have wider support on older OS and systems. You would be surprised how many devices offer up an unfiltered network interface when you plug one in! I have several of the Plugable ones from Amazon that have lasted well.
USB WiFi adapter
For WiFi connected devices, you will want to make a hotspot on your machine. For this, you need a USB WiFi adapter that can act as an access point.
I have a stock of TP-Link TL-WN722N, but only the V1 is suitable for this. The readily available Alfa devices are suitable as well.
USB Logic analyser
A logic analyser allows you to monitor multiple digital signals at the same time. There are a lot of options on the market here.
Generally, when reverse engineering, you are looking at signals over a long period of time. SPI, serial, I2C. You favour sample length, convenience and the ability to quickly export data to files for post-processing.
It’s for this reason that I prefer USB logic analysers. They facilitate reverse engineering. Dedicated instruments with screens are more useful for timing issues and lots of parallel channels.
Professionally, we all use Saleae Logic Pro 16. They are, however, expensive. The analog inputs, whilst helpful from time-to-time, are not strictly required.
At the opposite end of the market are the low-cost Hobby Components devices. 8 channels are adequate for a lot of work, but the 24MHz sample rate can be limiting when dealing with faster signals. They often struggle to get even 10MHz on many laptops. Adequate for serial ports, but not SPI.
With all of these USB devices, you are going to want a USB hub. Not only do these give you more ports, but they provide a degree of isolation between your laptop and the device you are working on.
The Sabrent switched hub from Amazon is great. This has individual power switches per-port, allowing you to quickly power cycle devices. If you have ever worked with USB in a Linux VM, you will quickly see why this is desirable!
The part missing from this post is making connections to devices. They don’t have pin headers fitted all of the time. That’s coming up.