In default GPIO4 mode can be used with WsprryPi, SSTV, CW, check manual here: j.mp/tapr-qrpi GPIO4 mode works with RPi 1 B, B+ and RPi 2 as well for WSPR mode.
When using in the experimental GPIO18 mode (solder jumper selectable; SSB USB, LSB, NFM, WFM, AM with qtcsdr and rpitx) it works only with RPi 2 right now (due to CPU demand)
I’m adding GPIO18 option for experimental mode only to use with qtcsdr and rpitx! By default the solder jumper is set for GPIO4 by short cut. As for VFO operation (CW signal) GPIO18 works nice but not yet tested comprehensively for other modulation yet, please take care of this in shake of RF spectrum emission!
The QRPi shield is available at TAPR’s webshop: https://www.tapr.org/kits_20M-wspr-pi.html
Thanks for your interest!