I believe from reading some of the existing posts that my JLink EDU mini programmer (with SWD connection) should work with the nRF51822 (it shows up as a device option in the configuration menus). Can I use the JFlash Lite program, in lieu of the nRF Connect Programmer, to flash the nRF Sniffer firmware to the board? If so, what should the starting memory address be and what SWD transfer speed can be used?
You can download and use 'nrfjprog' from:https://www.nordicsemi.com/Software-and-tools/Development-Tools/nRF-Command-Line-Tools/Download
To program the hex file call 'nrfjprog --eraseall' followed by 'nrfjprog --program the_hex_file.hex'.
The start address is in the hex file, so nothing you should change. Default programming speed should be fine.
Would the Programmer tool that is part of the nRF Connect for Desktop package (which I already have installed) also work, or is that only for boards with on-board JLink hardware?
I think there is some check that it's an nRF DK, but you can give it a go, it may work. You need to connect GND, SWDIO, SWDCLK, and VDD (fixed 3V I think, since the jlink mini only support 3V?).
After attaching an SWD connector to the nRF51822 device I was able to program it with the nRF Connect for Desktop, Programmer module and the JLink EDU mini programmer. The JLink mini showed up as a selectable device and after browsing to the desired HEX file, with the Add HEX file option, the Erase & write option loaded the hex file into memory with no problems. I installed the nRF Sniffer V3 firmware, in place of pre-installed nRF Sniffer V2 beta firmware, and the device appears to be working well. The only glitch is that the blue led on the device no longer lights up, even when I go back to the V2 beta firmware that was supposed to be pre-loaded. However, I don't see how this could be the result of using the nRF Connect for Desktop, Programmer module or the JLink EDU mini.