diff --git a/firmware/rtl/autoapproach/autoapproach_sim.cpp b/firmware/rtl/autoapproach/autoapproach_sim.cpp
deleted file mode 100644
index 9412b30..0000000
--- a/firmware/rtl/autoapproach/autoapproach_sim.cpp
+++ /dev/null
@@ -1,125 +0,0 @@
-#include <random>
-#include <cmath>
-
-#include "Vautoapproach_sim.h"
-#include "../testbench.hpp"
-
-/* TODO: generalize so bram_interface_sim can use it.
- * This should make a triangle wave.
- */
-class RefreshModule {
-	uint32_t *store_32;
-	size_t word_amnt;
-	bool pending_refresh_start;
-
-	public:
-	void posedge(uint8_t &refresh_start, uint32_t &start_addr,
-	             uint8_t refresh_finished) {
-		if (refresh_start && refresh_finished) {
-			refresh_start = 0;
-		} else if (pending_refresh_start && !refresh_start) {
-			pending_refresh_start = false;
-			refresh_start = 1;
-		}
-	}
-
-	RefreshModule(size_t _word_amnt, size_t _start_addr)
-	: word_amnt{_word_amnt}
-	, start_addr{_start_addr} {
-		store_32 = new uint32_t[_start_addr];
-		for (size_t i = 0; i < start_addr; i++) {
-			/* 0xFFFFF is the maximum DAC value */
-			store_32[i] = 0xFFFFF*max(double)i/start_addr;
-		}
-		pending_refresh_start = true;
-	}
-
-	~RefreshModule() {
-		delete[] store_32;
-	}
-};
-
-/* TODO: make generic SPI delay class because this code has been duplicated
- * many times over now. This function is also similar to the control loop
- * ADC simulation. */
-class GaussianZPiezo {
-	std::default_random_engine generator;
-	std::normal_distribution<> dist;
-	double scale;
-	double setpt;
-	double midpt;
-	double stretch;
-
-	double sample() {return scale*dist(generator);}
-
-	GaussianZPiezo(double scale, double mean, double dev, double setpt,
-	               double midpt, double stretch, int seed,
-	               uint16_t dac_wait_count,
-	               uint16_t adc_wait_count)
-	: scale{scale}, dist{mean,dev}, generator{},
-	, setpt{setpt}, midpt{midpt}, stretch{stretch},
-	, dac_wait_count_max{dac_wait_count}
-	, adc_wait_count_max{adc_wait_count} {
-		if (seed < 0) {
-			std::random_device rd;
-			generator.seed(rd());
-		} else {
-			generator.seed(seed);
-		}
-	}
-	/* Sigmoid function. This function is
-
-	                c(x-d)
-	f(x) = A*-------------------
-	          sqrt(1+(c(x-d))^2)
-
-	where A is the setpoint and c is how compressed the sigmoid is.
-	*/
-
-	double f(uint32_t x) {
-		double x_shift = x - midpt + sample();
-		return setpt*stretch*x_shift/sqrt(fma(x_shift,x_shift,1));
-	}
-
-	public:
-
-	void posedge(uint8_t &dac_finished, uint8_t dac_arm,
-	             uint32_t dac_out,
-	             uint8_t &adc_finished, uint8_t adc_arm,
-	             uint32_t &adc_out) {
-		if (adc_arm && adc_wait_counter == adc_wait_counter_max &&
-		    !adc_finished) {
-			adc_finished = 1;
-			adc_out = sample();
-		} else if (!adc_arm) {
-			adc_finished = 0;
-			adc_wait_counter = 0;
-		} else {
-			adc_wait_counter++;
-		}
-
-		if (dac_arm && dac_wait_counter == dac_wait_counter_max &&
-		    !dac_finished) {
-			dac_finished = 1;
-	}
-};
-
-class AA_TB : TB<Vautoapproach_sim> {
-	RefreshModule refresh;
-	GaussianZPiezo piezo;
-
-	void posedge() override;
-	AA_TB(size_t word_amnt, uint32_t start_addr)
-	: refresh{word_amnt, start_addr} {}
-
-	~AA_TB() {}
-};
-
-AA_TB::posedge() {
-	refresh.posedge(mod.refresh_start, mod.start_addr,
-	                mod.refresh_finished);
-}
-
-int main(int argc, char **argv) {
-	return 0;
-}
diff --git a/firmware/rtl/autoapproach/autoapproach_sim.v b/firmware/rtl/autoapproach/autoapproach_sim.v
deleted file mode 100644
index 592f616..0000000
--- a/firmware/rtl/autoapproach/autoapproach_sim.v
+++ /dev/null
@@ -1,96 +0,0 @@
-module autoapproach_sim #(
-	parameter DAC_WID = 24,
-	parameter DAC_DATA_WID = 20,
-	parameter ADC_WID = 24,
-	parameter TIMER_WID = 32,
-	parameter WORD_WID = 24,
-	parameter WORD_AMNT_WID = 11,
-	parameter [WORD_AMNT_WID-1:0] WORD_AMNT = 2047,
-	parameter RAM_WID = 32,
-	parameter RAM_WORD_WID = 16,
-	parameter RAM_WORD_INCR = 2,
-	parameter TOTAL_RAM_WORD_MINUS_ONE = 4095
-) (
-	input clk,
-	input arm,
-	output stopped,
-	output detected,
-
-	input polarity,
-	input [ADC_WID-1:0] setpoint,
-	input [TIMER_WID-1:0] time_to_wait,
-
-	/* User interface */
-	input refresh_start,
-	input [RAM_WID-1:0] start_addr,
-	output refresh_finished,
-
-	/* DAC wires. */
-	input dac_finished,
-	output dac_arm,
-	output [DAC_WID-1:0] dac_out,
-
-	input adc_finished,
-	output adc_arm,
-	input [ADC_WID-1:0] measurement
-
-	input[RAM_WORD_WID-1:0] backing_store [TOTAL_RAM_WORD_MINUS_ONE:0]
-);
-
-wire [RAM_WID-1:0] ram_dma_addr;
-wire [RAM_WORD_WID-1:0] ram_word;
-wire ram_read;
-wire ram_valid;
-
-dma_sim #(
-	.RAM_WID(RAM_WID),
-	.RAM_WORD_WID(RAM_WORD_WID),
-	.RAM_REAL_START(RAM_REAL_START),
-	.RAM_CNTR_LEN(RAM_CNTR_LEN),
-	.TOTAL_RAM_WORD_MINUS_ONE(TOTAL_RAM_WORD_MINUS_ONE),
-	.DELAY_CNTR_LEN(DELAY_CNTR_LEN),
-	.DELAY_TOTAL(DELAY_TOTAL)
-) dma_sim (
-	.clk(clk),
-	.ram_dma_addr(ram_dma_addr),
-	.ram_word(ram_word),
-	.ram_read(ram_read),
-	.ram_valid(ram_valid),
-	.backing_store(backing_store)
-);
-
-autoapproach #(
-	.DAC_WID(DAC_WID),
-	.DAC_DATA_WID(DAC_DATA_WID),
-	.ADC_WID(ADC_WID),
-	.TIMER_WID(TIMER_WID),
-	.WORD_WID(WORD_WID),
-	.WORD_AMNT_WID(WORD_AMNT_WID),
-	.WORD_AMNT(WORD_AMNT),
-	.RAM_WID(RAM_WID),
-	.RAM_WORD_WID(RAM_WORD_WID),
-	.RAM_WORD_INCR(RAM_WORD_INCR)
-) aa (
-	.clk(clk),
-	.arm(arm),
-	.stopped(stopped),
-	.detected(detected),
-	.polarity(polarity),
-	.setpoint(setpoint),
-	.time_to_wait(time_to_wait),
-	.refresh_start(refresh_start),
-	.start_addr(start_addr),
-	.refresh_finished(refresh_finished),
-	.ram_dma_addr(ram_dma_addr),
-	.ram_word(ram_word),
-	.ram_read(ram_read),
-	.ram_valid(ram_valid),
-	.dac_finished(dac_finished),
-	.dac_arm(dac_arm),
-	.dac_out(dac_out),
-	.adc_finished(adc_finished),
-	.adc_arm(adc_arm),
-	.measurement(measurement)
-);
-
-endmodule
diff --git a/firmware/rtl/spi/spi_switch.v b/firmware/rtl/spi/spi_switch.v
index 60c2e61..0616d94 100644
--- a/firmware/rtl/spi/spi_switch.v
+++ b/firmware/rtl/spi/spi_switch.v
@@ -4,7 +4,7 @@
  * This crossbar is entirely controlled by the kernel.
  */
 module spi_crossbar #(
-	parameter PORTS = 2,
+	parameter PORTS = 8,
 (
 	input select[PORTS-1:0],
 
@@ -23,19 +23,27 @@ module spi_crossbar #(
    Do things the old, dumb way instead.
  */
 
-always @(*) begin
-	if (select[1]) begin
-		mosi = mosi_ports[1];
-		miso = miso_ports[1];
-		sck = sck_ports[1];
-		ss = ss_ports[1];
-	end else begin
-		/* Select zeroth slot by default. No latches. */
-		mosi = mosi_ports[0];
-		miso = miso_ports[0];
-		sck = sck_ports[0];
-		ss = ss_ports[0];
+`define do_select(n)           \
+	mosi = mosi_ports[n];  \
+	miso = miso_ports[n];  \
+	sck = sck_ports[n];    \
+	ss = ss_ports[n]
+
+`define check_select(n)        \
+	if (select[n]) begin   \
+		do_select(n);  \
 	end
+
+always @(*) begin
+	check_select(7)
+	else check_select(6)
+	else check_select(5)
+	else check_select(4)
+	else check_select(3)
+	else check_select(2)
+	else check_select(1)
+	else do_select(0)
 end
 
 endmodule
+`undefineall
diff --git a/firmware/rtl/autoapproach/Makefile b/firmware/rtl/waveform/Makefile
similarity index 100%
rename from firmware/rtl/autoapproach/Makefile
rename to firmware/rtl/waveform/Makefile
diff --git a/firmware/rtl/autoapproach/bram_dma.cpp b/firmware/rtl/waveform/bram_dma.cpp
similarity index 100%
rename from firmware/rtl/autoapproach/bram_dma.cpp
rename to firmware/rtl/waveform/bram_dma.cpp
diff --git a/firmware/rtl/autoapproach/bram_dma.hpp b/firmware/rtl/waveform/bram_dma.hpp
similarity index 100%
rename from firmware/rtl/autoapproach/bram_dma.hpp
rename to firmware/rtl/waveform/bram_dma.hpp
diff --git a/firmware/rtl/autoapproach/bram_interface.v b/firmware/rtl/waveform/bram_interface.v
similarity index 100%
rename from firmware/rtl/autoapproach/bram_interface.v
rename to firmware/rtl/waveform/bram_interface.v
diff --git a/firmware/rtl/autoapproach/bram_interface_sim.cpp b/firmware/rtl/waveform/bram_interface_sim.cpp
similarity index 100%
rename from firmware/rtl/autoapproach/bram_interface_sim.cpp
rename to firmware/rtl/waveform/bram_interface_sim.cpp
diff --git a/firmware/rtl/autoapproach/bram_interface_sim.v b/firmware/rtl/waveform/bram_interface_sim.v
similarity index 100%
rename from firmware/rtl/autoapproach/bram_interface_sim.v
rename to firmware/rtl/waveform/bram_interface_sim.v
diff --git a/firmware/rtl/autoapproach/dma_sim.v b/firmware/rtl/waveform/dma_sim.v
similarity index 100%
rename from firmware/rtl/autoapproach/dma_sim.v
rename to firmware/rtl/waveform/dma_sim.v
diff --git a/firmware/rtl/autoapproach/autoapproach.v b/firmware/rtl/waveform/waveform.v
similarity index 67%
rename from firmware/rtl/autoapproach/autoapproach.v
rename to firmware/rtl/waveform/waveform.v
index 1d9f244..473a095 100644
--- a/firmware/rtl/autoapproach/autoapproach.v
+++ b/firmware/rtl/waveform/waveform.v
@@ -1,12 +1,13 @@
-/* Autoapproach module. This module applies a waveform located in memory
- * (and copied into Block RAM). This waveform is arbitrary but of fixed
- * length.
- * time in between sent sample, total period 10-50ms
- */
-module autoapproach #(
+/* Write a waveform to a DAC. */
+module waveform #(
 	parameter DAC_WID = 24,
-	parameter DAC_DATA_WID = 20,
-	parameter ADC_WID = 24,
+	parameter DAC_WID_SIZ = 5,
+	parameter DAC_POLARITY = 0,
+	parameter DAC_PHASE = 1,
+	parameter DAC_CYCLE_HALF_WAIT = 10,
+	parameter DAC_CYCLE_HALF_WAIT_SIZ = 4,
+	parameter DAC_SS_WAIT = 5,
+	parameter DAC_SS_WAIT_SIZ = 3,
 	parameter TIMER_WID = 32,
 	parameter WORD_WID = 24,
 	parameter WORD_AMNT_WID = 11,
@@ -17,11 +18,6 @@ module autoapproach #(
 ) (
 	input clk,
 	input arm,
-	output stopped,
-	output detected,
-
-	input polarity,
-	input [ADC_WID-1:0] setpoint,
 	input [TIMER_WID-1:0] time_to_wait,
 
 	/* User interface */
@@ -36,15 +32,18 @@ module autoapproach #(
 	input ram_valid,
 
 	/* DAC wires. */
-	input dac_finished,
-	output dac_arm,
-	output [DAC_WID-1:0] dac_out,
-
-	input adc_finished,
-	output adc_arm,
-	input [ADC_WID-1:0] measurement
+	input miso,
+	output mosi,
+	input sck,
+	output ss_L
 );
 
+wire [WORD_WID-1:0] word;
+reg word_next;
+wire word_ok;
+wire word_last;
+wire word_rst;
+
 bram_interface #(
 	.WORD_WID(WORD_WID),
 	.WORD_AMNT_WID(WORD_AMNT_WID),
@@ -59,22 +58,46 @@ bram_interface #(
 	.word_last(word_last),
 	.word_ok(word_ok),
 	.word_rst(word_rst),
+
 	.refresh_start(refresh_start),
 	.start_addr(start_addr),
 	.refresh_finished(refresh_finished),
+
 	.ram_dma_addr(ram_dma_addr),
 	.ram_word(ram_word),
 	.ram_read(ram_read),
 	.ram_valid(ram_valid)
 );
 
+wire dac_finished;
+reg dac_arm;
+reg [DAC_WID-1:0] dac_out;
+
+spi_master_ss_no_read #(
+	.WID(DAC_WID),
+	.WID_LEN(DAC_WID_SIZ),
+	.CYCLE_HALF_WAIT(DAC_CYCLE_HALF_WAIT),
+	.TIMER_LEN(DAC_CYCLE_HALF_WAIT_SIZ),
+	.POLARITY(DAC_POLARITY),
+	.PHASE(DAC_PHASE),
+	.SS_WAIT(DAC_SS_WAIT),
+	.SS_WAIT_TIMER_LEN(DAC_SS_WAIT_SIZ)
+) dac_master (
+	.clk(clk),
+	.mosi(mosi),
+	.miso(miso),
+	.sck_wire(sck),
+	.ss_L(ss_L),
+	.finished(dac_finished),
+	.arm(dac_arm),
+	.to_slave(dac_out)
+);
+
 localparam WAIT_ON_ARM = 0;
 localparam DO_WAIT = 1;
 localparam RECV_WORD = 2;
 localparam WAIT_ON_DAC = 3;
-localparam WAIT_ON_DETECTION = 4;
-localparam DETECTED = 5;
-reg [2:0] state = WAIT_ON_ARM;
+reg [1:0] state = WAIT_ON_ARM;
 
 reg [TIMER_WID-1:0] wait_timer = 0;
 
@@ -107,23 +130,10 @@ WAIT_ON_DAC: if (dac_finished) begin
 	dac_arm <= 0;
 	/* Was the last word read *the* last word? */
 	if (word_last) begin
-		state <= WAIT_ON_DETECTION;
-		adc_arm <= 1;
-	end else begin
 		state <= WAIT_ON_ARM;
+	end else begin
+		state <= DO_WAIT;
 	end
 endcase
-WAIT_ON_DETECTION: if (adc_finished) begin
-	if ((polarity && measurement >= setpt) ||
-	    (!polarity && measurement <= setpt)) begin
-		state <= DETECTED;
-		detected <= 1;
-	end
-end
-DETECTED: if (!arm) begin
-	state <= WAIT_ON_ARM;
-	detected <= 0;
-end
-endcase
 
 endmodule