The Black Magic Probe is really nice. If you want to try it out without spending the money for a BMP up front, it's also fairly simple to flash it onto a Blue P

The Black Magic Probe is really nice. If you want to try it out without spending the money for a BMP up front, it's also fairly simple to flash it onto a Blue Pill board that can be had for a few dollars. Most F103C8 Blue Pills are sold as having 64KB flash, but actually have 128KB flash. E.g. I installed BMP on a RobotDyn Blue Pill without any problems. Of course, if you like the BMP, it is worthwhile to buy the real thing to sponsor 1 Bit Squared and the convenient headers/cables.