Add center_halfway flag

src/readouts/ADCs.jl

@@ -11,11 +11,12 @@ Adds a readout event with `nsamples` readouts.
 
 ## Parameters
 - `nsamples`: number of samples in the readout.
+- `center_halfway`: by default the `time_to_center` is assumed to be half of the `duration`. Set this to false to disable this assumption.
 
 ## Variables
 - `dwell_time`: Time between each readout sample in ms.
 - `duration`: Total duration of the ADC event in ms.
-- `time_to_center`: time till the center of k-space (assumed to be `duration/2` if not set explicitly).
+- `time_to_center`: time till the center of k-space.
 """
 struct ADC <: BuildingBlock
     nsamples :: Integer
@@ -23,18 +24,18 @@ struct ADC <: BuildingBlock
     time_to_center :: Union{Nothing, VariableType}
 end
 
-function ADC(nsamples; dwell_time=nothing, time_to_center=nothing, kwargs...)
+function ADC(nsamples; dwell_time=nothing, time_to_center=nothing, center_halfway=true, kwargs...)
     res = ADC(
         nsamples,
         get_free_variable(dwell_time),
-        time_to_center isa VariableType ? time_to_center : nothing
+        get_free_variable(time_to_center),
     )
     @constraint global_model() res.dwell_time >= 0
-    if time_to_center isa VariableType
-        @constraint global_model() time_to_center >= 0
-        @constraint global_model() time_to_center <= duration(res)
+    if center_halfway
+        @constraint global_model() 2 * res.time_to_center == duration(res)
     else
-        apply_simple_constraint!(effective_time(res), time_to_center)
+        @constraint global_model() res.time_to_center >= 0
+        @constraint global_model() res.time_to_center <= duration(res)
     end
     set_simple_constraints!(res, kwargs)
     return res
@@ -42,9 +43,9 @@ end
 
 dwell_time(adc::ADC) = adc.dwell_time
 duration(adc::ADC) = adc.nsamples * dwell_time(adc)
-time_to_center(adc::ADC) = isnothing(adc.time_to_center) ? duration(adc) / 2 : adc.time_to_center
+time_to_center(adc::ADC) = adc.time_to_center
 effective_time(adc::ADC) = time_to_center(adc)
 
-variables(::Type{<:ADC}) = [dwell_time, duration, effective_time]
+variables(::Type{<:ADC}) = [dwell_time, duration, time_to_center]
 
 end
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