I home to max and then probe the bed at the start of the print. I'm using a Precision Piezo20 for the probing.
Relevant parts of my startup gcode
G28 ; home
G1 X200 Y200 Z5 ; Move close to center of the bed
M109 S160 ; set the hotend temperature for probing and wait
G30 ; Simple probe of the bed to set 0 and squish any drool
G30 ; do it again rule out any squish
G29 S1 ; Load the bed height map
My Config
; Configuration file for Duet WiFi (firmware version 1.20 or newer)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool on Sat Feb 17 2018 18:30:50 GMT-0500 (EST)
; General preferences
M111 S0 ; Debugging off
G21 ; Work in millimetres
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves
M555 P1 ; Set firmware compatibility to look like RepRapFirmare
; Network
M550 PCoreXY ; Set machine name
M552 S1 ; Enable network
;*** Access point is configured manually via M587
M586 P0 S1 ; Enable HTTP
M586 P1 S0 ; Disable FTP
M586 P2 S0 ; Disable Telnet
M667 S1 ; Select CoreXY mode
M208 X0 Y0 Z-5 S1 ; Set axis minima
M208 X400 Y400 Z444 S0 ; Set axis maxima
; Endstops
M574 X1 Y2 Z2 S0 ; Set active low endstops
; Z Probe
M558 P5 I1 R0.9 F360 T1000 A3 ; Set Z probe type to switch and the dive height + speeds
G31 X0 Y0 Z-0.15 P600 ; Set Z probe trigger value, offset and trigger height
; Define mesh grid
M557 X40:360 Y40:360 S32
; Drives
M569 P0 S0 ; Drive 0 goes backwards
M569 P1 S0 ; Drive 1 goes backwards
M569 P2 S0 ; Drive 2 goes backwards
M569 P3 S1 ; Drive 3 goes forwards
M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
M92 X80 Y80 Z1600 E838 ; Set steps per mm // 1.8 stepper 419
M566 X500 Y500 Z12 E1200 ; Set maximum instantaneous speed changes (mm/min)
M203 X18000 Y18000 Z1250 E3600 ; Set maximum speeds (mm/min)
M201 X1600 Y1600 Z300 E1500 ; Set accelerations (mm/s^2)
M906 X1480 Y1480 Z1500 E1200 I15 ; Set motor currents (mA) and motor idle factor in percent (1.8 stepper extruder E600)
M84 S30 ; Set idle timeout
; Heated Bed
M307 H0 A202.0 C457.0 D1.6 S0.80 V24.0 B0 ; PID settings
M305 P0 T99904 B3932 C8.791829e-8 R4700 ; Set thermistor + ADC parameters for heater 0
M143 H0 S140 ; Set temperature limit for heater 0 to 140C
; Hotend
M307 H1 A472.5 C292.1 D5.2 S0.95 V24.0 B0 ; PID settings
M305 P1 X200 ; Use RTD 0
M143 H1 S280 ; Set temperature limit for heater 1 to 280C
M207 S0.80 F2400 Z0.30 ; Firmware retraction .8mm, 40 mm/s, z hop of 0.30
; Tools
M563 P0 D0 H1 ; Define tool 0
G10 P0 X0 Y0 Z0 ; Set tool 0 axis offsets
G10 P0 R0 S0 ; Set initial tool 0 active and standby temperatures to 0C
; Fans
M106 P0 S0 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
;M106 P1 S255 I0 F20 H1 T55 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
M106 P1 S255 I0 F500 H1 T55 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
M106 P2 S0 I0 F500 H-1 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned off
; Load the bed mapping file automatically
G29 S1
; Automatic saving after power loss is not enabled
; Custom settings are not configured
M912 P0 S-7.1 ; Offset CPU temperature
T0 ; Select Extruder
