diff --git a/firmware/rtl/raster/raster.v b/firmware/rtl/raster/raster.v
index c994710..9fb766a 100644
--- a/firmware/rtl/raster/raster.v
+++ b/firmware/rtl/raster/raster.v
@@ -5,6 +5,7 @@
  * The kernel then reads these values and sends them to the controller
  * over ethernet.
  */
+`include "raster_cmds.vh"
 module raster #(
 	parameter SAMPLEWID = 9,
 	parameter DAC_DATA_WID = 20,
@@ -16,21 +17,13 @@ module raster #(
 	parameter MAX_ADC_DATA_WID = 24
 ) (
 	input clk,
-	input arm,
-	output reg finished,
-	output reg running,
 
-	/* Amount of samples in one line (forward) */
-	input [SAMPLEWID-1:0] max_samples_in,
-	/* Amount of lines in the output. */
-	input [SAMPLEWID-1:0] max_lines_in,
-	/* Wait time after each step. */
-	input [TIMER_WID-1:0] settle_time_in,
-
-	/* Each step goes (x,y) -> (x + dx, y + dy) forward for each line of
-	 * the output. */
-	input signed [DAC_DATA_WID-1:0] dx_in,
-	input signed [DAC_DATA_WID-1:0] dy_in,
+	/* Kernel interface. */
+	input [`RASTER_CMD_WID-1:0] kernel_cmd,
+	input [`RASTER_DATA_WID-1:0] kernel_data_in,
+	output reg [`RASTER_DATA_WID-1:0] kernel_data_out,
+	input kernel_ready,
+	output reg kernel_finished,
 
 	/* X and Y DAC piezos */
 	output x_arm,
@@ -54,9 +47,6 @@ module raster #(
 	input [ADCNUM*MAX_ADC_DATA_WID-1:0] adc_data,
 	input [ADCNUM-1:0] adc_finished,
 
-	/* Bitmap for which ADCs are used. */
-	input [ADCNUM-1:0] adc_used_in,
-
 	/* RAM DMA. This is generally not directly connected to the
 	 * DMA IP. A shim is used in order to write multiple words
 	 * to memory. */
@@ -114,11 +104,10 @@ localparam GET_DAC_VALUES = 1;
 localparam REQUEST_DAC_VALUES = 2;
 localparam MEASURE = 3;
 localparam SCAN_ADC_VALUES = 4;
-localparam SEND_VALUE = 5;
-localparam ADVANCE_DAC_WRITE = 6;
-localparam WAIT_ADVANCE = 7;
-localparam NEXT_LINE  = 9;
-localparam WAIT_ON_ARM_DEASSERT = 10;
+localparam ADVANCE_DAC_WRITE = 5;
+localparam WAIT_ADVANCE = 6;
+localparam NEXT_LINE  = 7;
+localparam WAIT_ON_ARM_DEASSERT = 8;
 localparam STATE_WID = 4;
 
 /********** Loop State ***********/
@@ -134,26 +123,13 @@ reg signed [DAC_DATA_WID-1:0] y_val = 0;
  * which ADC values should be read off.
  */
 reg [ADCNUM-1:0] adc_used_tmp = 0;
-
-/* Buffer to store ADC data. The buffers are permuted in order
- * for the design to read off the proper values into RAM.
- */
-reg [MAX_ADC_DATA_WID-1:0] adc_data_tmp [ADCNUM-1:0];
-
-genvar ii;
-generate for (ii = 0; ii < ADCNUM - 1; ii = ii + 1) begin
-	always @ (posedge clk) begin
-		if (state == SCAN_ADC_VALUES) begin
-			adc_data_tmp[ii] <= adc_data_tmp[ii+1];
-		end else if (state == MEASURE && adc_finished == adc_arm) begin
-			adc_data_tmp[ii] <= adc_data[(ADCNUM-ii)*MAX_ADC_DATA_WID-1:(ADCNUM-ii-1)*MAX_ADC_DATA_WID];
-		end
-	end
-end endgenerate
+reg [ADCNUM*MAX_ADC_DATA_WID-1:0] adc_data_tmp = 0;
 
 /********** Loop Parameters *************/
 reg [ADCNUM-1:0] adc_used = 0;
 reg is_reverse = 0;
+reg arm = 0;
+reg running = 0;
 reg signed [DAC_DATA_WID-1:0] dx = 0;
 reg signed [DAC_DATA_WID-1:0] dy = 0;
 reg [TIMER_WID-1:0] settle_time = 0;
@@ -162,16 +138,73 @@ reg [SAMPLEWID-1:0] max_samples = 0;
 reg [SAMPLEWID-1:0] max_lines = 0;
 reg [STEPWID-1:0] steps_per_sample = 0;
 
+/********** Control Interface ************ 
+ * This code assumes that RASTER_DATA_WID is greater than all registers.
+ * If a register is equal to the length, omit zero extension.
+ *
+ * This uses a macro since each register is exactly the same code, just
+ * with different length. The arm register is special: it can be adjusted
+ * while the loop is running (in order to terminate the scan), but
+ * otherwise each register can only be modified when the loop is not
+ * running.
+ */
+
+// Generates code to handle read requests from the kernel.
+`define generate_register_read(code, width, register)     \
+code: begin                                               \
+	kernel_data_out[(width)-1:0] <= register;         \
+	kernel_data_out[`RASTER_DATA_WID-1:(width)] <= 0; \
+	kernel_finished <= 1;                             \
+end
+
+// Generates code to handle write requests from the kernel.
+`define generate_register(code, width, register)         \
+`generate_register_read(code, width, register)           \
+code | `RASTER_WRITE_BIT: begin                          \
+	if (!running && (code) != `RASTER_ARM) begin     \
+		register <= kernel_data_in[(width)-1:0]; \
+		kernel_finished <= 1;                    \
+	end                                              \
+end
+
+always @ (posedge clk) begin
+	if (!kernel_ready) kernel_finished <= 0;
+	else if (kernel_ready) begin case (kernel_cmd)
+	`generate_register(`RASTER_MAX_SAMPLES, SAMPLEWID, max_samples)
+	`generate_register(`RASTER_MAX_LINES, SAMPLEWID, max_lines)
+	`generate_register(`RASTER_SETTLE_TIME, TIMER_WID, settle_time)
+	`generate_register(`RASTER_DX, DAC_DATA_WID, dx)
+	`generate_register(`RASTER_DY, DAC_DATA_WID, dy)
+	`generate_register(`RASTER_USED_ADCS, ADCNUM, adc_used)
+	`generate_register(`RASTER_STEPS_PER_SAMPLE, STEPWID, steps_per_sample)
+	`generate_register(`RASTER_ARM, 1, arm)
+	`generate_register_read(`RASTER_RUNNING, 1, running)
+	endcase end
+end
+`undef generate_register_read
+`undef generate_register
+
+task check_arm();
+	if (!arm) begin
+		state <= WAIT_ON_ARM;
+		running <= 0;
+	end
+endtask
+
+`ifdef VERILATOR
+task check_deassert_dac_arm();
+	if (x_arm) $error("x_arm asserted");
+	if (y_arm) $error("y_arm asserted");
+endtask
+`define CHECK_DAC_ARM check_deassert_dac_arm();
+`else
+`define CHECK_DAC_ARM
+`endif
+
 always @ (posedge clk) begin
 	case (state)
-	WAIT_ON_ARM: begin if (arm) begin
-		adc_used <= adc_used_in;
-		dx <= dx_in;
-		dy <= dy_in;
-		max_samples <= max_samples_in;
-		max_lines <= max_lines_in;
-		settle_time <= settle_time_in;
-
+	WAIT_ON_ARM: if (arm) begin
+		running <= 1;
 		is_reverse <= 0;
 		sample <= 0;
 		line <= 0;
@@ -182,22 +215,20 @@ always @ (posedge clk) begin
 		y_arm <= 1;
 
 		adc_arm <= 0;
-	end else begin
-		running <= 0;
-	end end
-	REQUEST_DAC_VALUES: begin
-		if (x_finished && y_finished) begin
-			x_to_dac <= 0;
-			y_to_dac <= 0;
-			x_arm <= 0;
-			y_arm <= 0;
-			state <= GET_DAC_VALUES;
-			counter <= 0;
-		end
+		state <= REQUEST_DAC_VALUES;
+	end
+	REQUEST_DAC_VALUES: if (x_finished && y_finished) begin
+		x_to_dac <= 0;
+		y_to_dac <= 0;
+		x_arm <= 0;
+		y_arm <= 0;
+		state <= GET_DAC_VALUES;
+		counter <= 0;
 	end
 	GET_DAC_VALUES: if (counter < DAC_WAIT_BETWEEN_CMD) begin
+		`CHECK_DAC_ARM
 		counter <= counter + 1;
-		if (!arm) state <= WAIT_ON_ARM;
+		check_arm();
 	end else if (!x_arm || !y_arm) begin
 		x_arm <= 1;
 		y_arm <= 1;
@@ -211,99 +242,90 @@ always @ (posedge clk) begin
 		state <= WAIT_ADVANCE;
 	end
 
-	WAIT_ADVANCE: begin
-		if (counter < settle_time) begin
-			if (!arm) state <= WAIT_ON_ARM;
-			counter <= counter + 1;
-		end else begin
-			adc_arm <= adc_used;
-			adc_used_tmp <= adc_used;
-			state <= MEASURE;
-		end
+	WAIT_ADVANCE: if (counter < settle_time) begin
+		check_arm();
+		counter <= counter + 1;
+		`CHECK_DAC_ARM
+	end else begin
+		`CHECK_DAC_ARM
+		adc_arm <= adc_used;
+		adc_used_tmp <= adc_used;
+		state <= MEASURE;
 	end
-	MEASURE: begin
-		if (adc_finished == adc_arm) begin
-			adc_arm <= 0;
-			state <= SCAN_ADC_VALUES;
-			counter <= 0;
-		end
+	MEASURE: if (adc_finished == adc_arm) begin
+		`CHECK_DAC_ARM
+		adc_arm <= 0;
+		adc_data_tmp <= adc_data;
+		state <= SCAN_ADC_VALUES;
+		counter <= 0;
 	end
-	SCAN_ADC_VALUES: begin
-		if (adc_used_tmp == 0) begin
-			if (sample == max_samples) begin
-				dx <= ~dx + 1;
-				dy <= ~dy + 1;
-				is_reverse <= !is_reverse;
-				sample <= 0;
+	SCAN_ADC_VALUES: if (adc_used_tmp == 0 && !mem_commit) begin
+		`CHECK_DAC_ARM
+		if (sample == max_samples) begin
+			dx <= ~dx + 1;
+			dy <= ~dy + 1;
 
-				if (is_reverse) begin
-					state <= NEXT_LINE;
-				end else begin
-					state <= ADVANCE_DAC_WRITE;
-				end
+			if (is_reverse) begin
+				state <= NEXT_LINE;
 			end else begin
 				state <= ADVANCE_DAC_WRITE;
 			end
+
+			is_reverse <= !is_reverse;
+			sample <= 0;
 		end else begin
-			adc_used_tmp <= adc_used_tmp << 1;
-			if (adc_used_tmp[ADCNUM-1]) begin
-				state <= SEND_VALUE;
-				data <= adc_data_tmp[ADCNUM-1];
-				mem_commit <= 1;
-			end
+			state <= ADVANCE_DAC_WRITE;
+		end
+	end else if (mem_finished) begin
+		`CHECK_DAC_ARM
+		state <= SCAN_ADC_VALUES;
+		mem_commit <= 0;
+	end else begin
+		`CHECK_DAC_ARM
+		adc_used_tmp <= adc_used_tmp << 1;
+		adc_data_tmp <= adc_data_tmp << MAX_ADC_DATA_WID;
+		if (adc_used_tmp[ADCNUM-1]) begin
+			data <= adc_data_tmp[ADCNUM*MAX_ADC_DATA_WID-1:(ADCNUM-1)*MAX_ADC_DATA_WID];
+			mem_commit <= 1;
 		end
 	end
 
-	SEND_VALUE: if (mem_finished) begin
-		if (!arm) state <= WAIT_ON_ARM;
-		else state <= SCAN_ADC_VALUES;
+	ADVANCE_DAC_WRITE: if (!x_arm || !y_arm) begin
+		x_val <= x_val + dx;
+		y_val <= y_val + dy;
+		x_to_dac <= {4'b0001, x_val + dx};
+		y_to_dac <= {4'b0001, y_val + dy};
+		x_arm <= 1;
+		y_arm <= 1;
+		sample <= sample + 1;
+	end else if (x_finished && y_finished) begin
+		counter <= 0;
+		state <= WAIT_ADVANCE;
+		x_arm <= 0;
+		y_arm <= 0;
 	end
-	ADVANCE_DAC_WRITE: begin
-		if (!x_arm || !y_arm) begin
-			x_val <= x_val + dx;
-			y_val <= y_val + dy;
-			x_to_dac <= {4'b0001, x_val + dx};
-			y_to_dac <= {4'b0001, y_val + dy};
+	NEXT_LINE: if (!x_arm || !y_arm) begin
+		if (line == max_lines) begin
+			state <= WAIT_ON_ARM_DEASSERT;
+			running <= 0;
+		end else begin
+			/* rotation of (dx,dy) by 90° -> (dy, -dx) */
+			x_val <= x_val + dy;
+			x_to_dac <= {4'b0001, x_val + dy};
 			x_arm <= 1;
+			y_val <= y_val - dx;
+			y_to_dac <= {4'b0001, y_val - dx};
 			y_arm <= 1;
-			sample <= sample + 1;
-		end else if (x_finished && y_finished) begin
-			counter <= 0;
-			state <= WAIT_ADVANCE;
-			x_arm <= 0;
-			y_arm <= 0;
+			line <= line + 1;
 		end
+	end else if (x_finished && y_finished) begin
+		counter <= 0;
+		state <= WAIT_ADVANCE;
+		x_arm <= 0;
+		y_arm <= 0;
 	end
-
-	NEXT_LINE: begin
-		if (!x_arm && !y_arm) begin
-			if (line == max_lines) begin
-				state <= WAIT_ON_ARM_DEASSERT;
-				finished <= 1;
-				running <= 0;
-			end else begin
-				/* rotation of (dx,dy) by 90° -> (dy, -dx) */
-				x_val <= x_val + dy;
-				x_to_dac <= {4'b0001, x_val + dy};
-				x_arm <= 1;
-				y_val <= y_val - dx;
-				y_to_dac <= {4'b0001, y_val - dx};
-				y_arm <= 1;
-				line <= line + 1;
-			end
-		end else if (x_finished && y_finished) begin
-			counter <= 0;
-			state <= WAIT_ADVANCE;
-			x_arm <= 0;
-			y_arm <= 0;
-		end
-	end
-
-	WAIT_ON_ARM_DEASSERT: begin
-		if (!arm) begin
-			state <= WAIT_ON_ARM;
-			finished <= 0;
-		end
+	WAIT_ON_ARM_DEASSERT: if (!arm) begin
+		state <= WAIT_ON_ARM;
 	end
 	endcase
 end