Another minor success along my path of discovery - pressing the reset pin; causing a reset (funnily enough).
$ miniterm /dev/ttyAMA0 115200
--- Miniterm on /dev/ttyAMA0 115200,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
MSG:15,Vrms:245.22,P1:116,E1:4,pulse:1
emonTx V3 EmonLibCM Continuous Monitoring V1.50
OpenEnergyMonitor.org
No EEPROM setting found...using default values
Calibration:
vCal = 268.97
i1Cal = 90.90
i1Lead = 4.20
i2Cal = 90.90
i2Lead = 4.20
i3Cal = 90.90
i3Lead = 4.20
i4Cal = 16.67
i4Lead = 1.00
RFM69CW Node: 15 Freq: 433MHz Group: 210
RFM int...
'+++' then [Enter] now to enter config mode...5s
CT1 detected, i1Cal:90.90
AC present
MSG:1,Vrms:244.74,P1:116,E1:0,pulse:1
MSG:2,Vrms:244.70,P1:117,E1:0,pulse:1
MSG:3,Vrms:245.14,P1:116,E1:0,pulse:1