The IsoCore is a derivative of the pyboard. The IsoCore also employs an STM32F405RGT6 with support for a µUSB connection and µSD card, but without the accelerometer of the original pyboard.  The IsoCore breaks out I/O to headers by Port as well as to a PCIeX1 card-edge connector, tailored for a custom ecosystem.  It is intended (but there is no absolute need) to run microPython. As of 1.9.4, the stock image for the pyboard will work with the IsoCore after the 560R mod noted below.  It was developed primarily for this author's own personal ecosystem as a custom development tool.