diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3299ead..cf2c27b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,7 @@
 project(f107-fft C ASM)
 cmake_minimum_required(VERSION 3.5.0)
 
-file(GLOB_RECURSE USER_SOURCES "Src/*.c")
+file(GLOB_RECURSE USER_SOURCES "Src/*.c" "Max2719/*.c")
 file(GLOB_RECURSE HAL_SOURCES "Drivers/STM32F1xx_HAL_Driver/Src/*.c")
 
 add_library(HAL ${HAL_SOURCES})
@@ -13,12 +13,16 @@ include_directories(Inc)
 include_directories(Drivers/STM32F1xx_HAL_Driver/Inc)
 include_directories(Drivers/CMSIS/Include)
 include_directories(Drivers/CMSIS/Device/ST/STM32F1xx/Include)
+include_directories(Max2719)
+include_directories(/usr/arm-none-eabi/include)
+include_directories(/usr/lib/gcc/arm-none-eabi/6.1.1/include/)
+
 
 add_definitions(-DSTM32F107xC)
 add_definitions(-DUSE_FULL_ASSERT)
 add_executable(${PROJECT_NAME}.elf ${USER_SOURCES} ${LINKER_SCRIPT})
 
-target_link_libraries(${PROJECT_NAME}.elf HAL CMSIS)
+target_link_libraries(${PROJECT_NAME}.elf HAL CMSIS )
 
 set(HEX_FILE ${PROJECT_SOURCE_DIR}/build/${PROJECT_NAME}.hex)
 set(BIN_FILE ${PROJECT_SOURCE_DIR}/build/${PROJECT_NAME}.bin)
diff --git a/Inc/user_main.h b/Inc/user_main.h
index 8eb6e0f..343f4eb 100644
--- a/Inc/user_main.h
+++ b/Inc/user_main.h
@@ -11,4 +11,6 @@ void user_Error_Handler();
 
 void user_assert_failed(uint8_t* file, uint32_t line);
 
+void user_error_file_line(const char *message, const char *file, uint32_t line);
+
 #endif //F107_FFT_USER_MAIN_H
diff --git a/Max2719/dotmatrix.c b/Max2719/dotmatrix.c
new file mode 100644
index 0000000..fe848e4
--- /dev/null
+++ b/Max2719/dotmatrix.c
@@ -0,0 +1,129 @@
+#include <string.h>
+#include <stdbool.h>
+#include <utils.h>
+#include "dotmatrix.h"
+#include "malloc_safe.h"
+
+DotMatrix_Cfg* dmtx_init(DotMatrix_Init *init)
+{
+	DotMatrix_Cfg *disp = calloc_s(1, sizeof(DotMatrix_Cfg));
+
+	disp->drv.SPIx = init->SPIx;
+	disp->drv.CS_GPIOx = init->CS_GPIOx;
+	disp->drv.CS_PINx = init->CS_PINx;
+	disp->drv.chain_len = init->cols * init->rows;
+	disp->cols = init->cols;
+	disp->rows = init->rows;
+
+	disp->screen = calloc_s(init->cols * init->rows * 8, 1); // 8 bytes per driver
+
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_DECODE_MODE, 0x00); // no decode
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_SCAN_LIMIT, 0x07); // scan all 8
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_SHUTDOWN, 0x01); // not shutdown
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_DISPLAY_TEST, 0x00); // not test
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_INTENSITY, 0x07); // half intensity
+
+	// clear
+	for (uint8_t i = 0; i < 8; i++) {
+		max2719_cmd_all(&disp->drv, MAX2719_CMD_DIGIT0+i, 0);
+	}
+
+	return disp;
+}
+
+void dmtx_show(DotMatrix_Cfg* disp)
+{
+	for (uint8_t i = 0; i < 8; i++) {
+		// show each digit's array in turn
+		max2719_cmd_all_data(&disp->drv, MAX2719_CMD_DIGIT0+i, disp->screen + (i * disp->drv.chain_len));
+	}
+}
+
+void dmtx_clear(DotMatrix_Cfg* disp)
+{
+	memset(disp->screen, 0, disp->drv.chain_len*8);
+}
+
+void dmtx_intensity(DotMatrix_Cfg* disp, uint8_t intensity)
+{
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_INTENSITY, intensity & 0x0F);
+}
+
+void dmtx_blank(DotMatrix_Cfg* disp, bool blank)
+{
+	max2719_cmd_all(&disp->drv, MAX2719_CMD_SHUTDOWN, (!blank) & 0x01);
+}
+
+/**
+ * @brief Get a cell pointer
+ * @param disp : driver inst
+ * @param x : x coord
+ * @param y : y coord
+ * @param xd : pointer to store the offset in the cell
+ * @return cell ptr
+ */
+static uint8_t* cell_ptr(DotMatrix_Cfg* disp, int32_t x, int32_t y, uint8_t *xd)
+{
+	if (x < 0 || y < 0) return NULL;
+	if ((uint32_t)x >= disp->cols*8 || (uint32_t)y >= disp->rows*8) return NULL;
+
+	uint32_t cell_x = (uint32_t)x >> 3;
+	*xd = x & 7;
+
+	// resolve cell
+	uint32_t digit = y & 7;
+	cell_x += ((uint32_t)y >> 3) * disp->cols;
+
+	uint32_t cell_idx = (digit * disp->drv.chain_len) + cell_x;
+
+	return &disp->screen[cell_idx];
+}
+
+
+bool dmtx_get(DotMatrix_Cfg* disp, int32_t x, int32_t y)
+{
+	uint8_t xd;
+	uint8_t *cell = cell_ptr(disp, x, y, &xd);
+	if (cell == NULL) return 0;
+
+	return (*cell >> xd) & 1;
+}
+
+
+void dmtx_toggle(DotMatrix_Cfg* disp, int32_t x, int32_t y)
+{
+	uint8_t xd;
+	uint8_t *cell = cell_ptr(disp, x, y, &xd);
+	if (cell == NULL) return;
+
+	*cell ^= 1 << xd;
+}
+
+
+void dmtx_set(DotMatrix_Cfg* disp, int32_t x, int32_t y, bool bit)
+{
+	uint8_t xd;
+	uint8_t *cell = cell_ptr(disp, x, y, &xd);
+	if (cell == NULL) return;
+
+	if (bit) {
+		*cell |= 1 << xd;
+	} else {
+		*cell &= ~(1 << xd);
+	}
+}
+
+void dmtx_set_block(DotMatrix_Cfg* disp, int32_t startX, int32_t startY, uint32_t *data_rows, uint32_t width, uint16_t height)
+{
+	for (uint32_t y = 0; y < height; y++) {
+		uint32_t row = data_rows[y];
+
+		for (uint32_t x = 0; x < width; x++) {
+			int xx = startX + (int)x;
+			int yy = startY + (int)y;
+			bool val = (row >> (width - x - 1)) & 1;
+
+			dmtx_set(disp, xx, yy, val);
+		}
+	}
+}
diff --git a/Max2719/dotmatrix.h b/Max2719/dotmatrix.h
new file mode 100644
index 0000000..b61c7eb
--- /dev/null
+++ b/Max2719/dotmatrix.h
@@ -0,0 +1,63 @@
+#ifndef MATRIXDSP_H
+#define MATRIXDSP_H
+
+#include "stm32f1xx_hal.h"
+#include "max2719.h"
+#include <stdbool.h>
+
+
+typedef struct {
+	MAX2719_Cfg drv;
+	uint8_t *screen; /*!< Screen array, organized as series of [all #1 digits], [all #2 digits] ... */
+	uint32_t cols; /*!< Number of drivers horizontally */
+	uint32_t rows; /*!< Number of drivers vertically */
+} DotMatrix_Cfg;
+
+typedef struct {
+	SPI_TypeDef *SPIx; /*!< SPI iface used by this instance */
+	GPIO_TypeDef *CS_GPIOx; /*!< Chip select GPIO port */
+	uint16_t CS_PINx; /*!< Chip select pin mask */
+	uint32_t cols; /*!< Number of drivers horizontally */
+	uint32_t rows; /*!< Number of drivers vertically */
+} DotMatrix_Init;
+
+// global inst
+extern DotMatrix_Cfg *dmtx;
+
+
+DotMatrix_Cfg* dmtx_init(DotMatrix_Init *init);
+
+/**
+ * @brief Display the whole screen array
+ * @param dmtx : driver struct
+ */
+void dmtx_show(DotMatrix_Cfg* disp);
+
+/** Set intensity 0-16 */
+void dmtx_intensity(DotMatrix_Cfg* disp, uint8_t intensity);
+
+/** Display on/off */
+void dmtx_blank(DotMatrix_Cfg* disp, bool blank);
+
+/**
+ * @brief Send a single bit
+ * @param dmtx : driver struct
+ * @param x : pixel X
+ * @param y : pixel Y
+ * @param bit : 1 or 0
+ */
+void dmtx_set(DotMatrix_Cfg* disp, int32_t x, int32_t y, bool bit);
+
+/** Get a single bit */
+bool dmtx_get(DotMatrix_Cfg* disp, int32_t x, int32_t y);
+
+/** Set a block using array of row data */
+void dmtx_set_block(DotMatrix_Cfg* disp, int32_t startX, int32_t startY, uint32_t *data_rows, uint32_t width, uint16_t height);
+
+/** Toggle a single bit */
+void dmtx_toggle(DotMatrix_Cfg* disp, int32_t x, int32_t y);
+
+/** Clear the screen (not showing) */
+void dmtx_clear(DotMatrix_Cfg* disp);
+
+#endif // MATRIXDSP_H
diff --git a/Max2719/malloc_safe.c b/Max2719/malloc_safe.c
new file mode 100644
index 0000000..1e9036c
--- /dev/null
+++ b/Max2719/malloc_safe.c
@@ -0,0 +1,38 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <user_main.h>
+#include "malloc_safe.h"
+
+static void reset_when_done(void)
+{
+	//
+
+	HAL_NVIC_SystemReset();
+}
+
+
+void *malloc_safe_do(size_t size, const char* file, uint32_t line)
+{
+	void *mem = malloc(size);
+	if (mem == NULL) {
+		// malloc failed
+		user_error_file_line("Malloc failed", file, line);
+		reset_when_done();
+	}
+
+	return mem;
+}
+
+
+void *calloc_safe_do(size_t nmemb, size_t size, const char* file, uint32_t line)
+{
+	void *mem = calloc(nmemb, size);
+	if (mem == NULL) {
+		// malloc failed
+		user_error_file_line("Calloc failed", file, line);
+		reset_when_done();
+	}
+
+	return mem;
+}
diff --git a/Max2719/malloc_safe.h b/Max2719/malloc_safe.h
new file mode 100644
index 0000000..b5abec1
--- /dev/null
+++ b/Max2719/malloc_safe.h
@@ -0,0 +1,18 @@
+#ifndef MALLOC_SAFE_H
+#define MALLOC_SAFE_H
+
+/**
+ * Malloc that prints error and restarts the system on failure.
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include "stm32f1xx_hal.h"
+
+void *malloc_safe_do(size_t size, const char* file, uint32_t line);
+void *calloc_safe_do(size_t nmemb, size_t size, const char* file, uint32_t line);
+
+#define malloc_s(size)        malloc_safe_do(size,        __FILE__, __LINE__)
+#define calloc_s(nmemb, size) calloc_safe_do(nmemb, size, __FILE__, __LINE__)
+
+#endif // MALLOC_SAFE_H
diff --git a/Max2719/max2719.c b/Max2719/max2719.c
new file mode 100644
index 0000000..4efa15e
--- /dev/null
+++ b/Max2719/max2719.c
@@ -0,0 +1,81 @@
+#include <stdbool.h>
+#include <spi.h>
+#include "max2719.h"
+
+// TODO convert to buffer + batch write.
+// TODO store hspi in the max2719 struct, so it can be used.
+
+static inline
+void send_byte(MAX2719_Cfg *inst, uint8_t b)
+{
+	//inst->SPIx->DR = b;
+	//while (!(inst->SPIx->SR & SPI_SR_TXE));
+
+	// FIXME figure out why regular transmit is not working
+	HAL_SPI_Transmit(&hspi1, &b, 1, 10);
+}
+
+
+static inline
+void set_nss(MAX2719_Cfg *inst, bool nss)
+{
+	if (nss) {
+		inst->CS_GPIOx->BSRR = inst->CS_PINx;
+	} else {
+		inst->CS_GPIOx->BRR = inst->CS_PINx;
+	}
+}
+
+
+static void send_word(MAX2719_Cfg *inst, MAX2719_Command cmd, uint8_t data)
+{
+	send_byte(inst, cmd);
+	send_byte(inst, data);
+}
+
+
+void max2719_cmd(MAX2719_Cfg *inst, uint32_t nth, MAX2719_Command cmd, uint8_t data)
+{
+	set_nss(inst, 0);
+	while (inst->SPIx->SR & SPI_SR_BSY);
+
+	for (uint32_t i = 0; i < inst->chain_len; i++) {
+		if (i == inst->chain_len - nth - 1) {
+			send_word(inst, cmd, data);
+		} else {
+			send_word(inst, MAX2719_CMD_NOOP, 0);
+		}
+	}
+
+	while (inst->SPIx->SR & SPI_SR_BSY);
+	set_nss(inst, 1);
+}
+
+
+
+void max2719_cmd_all(MAX2719_Cfg *inst, MAX2719_Command cmd, uint8_t data)
+{
+	set_nss(inst, 0);
+	while (inst->SPIx->SR & SPI_SR_BSY);
+
+	for (uint32_t i = 0; i < inst->chain_len; i++) {
+		send_word(inst, cmd, data);
+	}
+
+	while (inst->SPIx->SR & SPI_SR_BSY);
+	set_nss(inst, 1);
+}
+
+
+void max2719_cmd_all_data(MAX2719_Cfg *inst, MAX2719_Command cmd, uint8_t *data)
+{
+	set_nss(inst, 0);
+	while (inst->SPIx->SR & SPI_SR_BSY);
+
+	for (uint32_t i = 0; i < inst->chain_len; i++) {
+		send_word(inst, cmd, data[inst->chain_len - i - 1]);
+	}
+
+	while (inst->SPIx->SR & SPI_SR_BSY);
+	set_nss(inst, 1);
+}
diff --git a/Max2719/max2719.h b/Max2719/max2719.h
new file mode 100644
index 0000000..373e94e
--- /dev/null
+++ b/Max2719/max2719.h
@@ -0,0 +1,61 @@
+#ifndef MAX2719_H
+#define MAX2719_H
+
+#include "stm32f1xx_hal.h"
+
+/** Generic utilities for controlling the MAX2719 display driver */
+
+typedef struct {
+	SPI_TypeDef *SPIx; /*!< SPI iface used by this instance */
+	GPIO_TypeDef *CS_GPIOx; /*!< Chip select GPIO port */
+	uint16_t CS_PINx; /*!< Chip select pin mask */
+	uint32_t chain_len; /*!< Number of daisy-chained drivers (for "all" or "n-th" commands */
+} MAX2719_Cfg;
+
+
+typedef enum {
+	MAX2719_CMD_NOOP = 0x00,
+
+	MAX2719_CMD_DIGIT0 = 0x01,
+	MAX2719_CMD_DIGIT1 = 0x02,
+	MAX2719_CMD_DIGIT2 = 0x03,
+	MAX2719_CMD_DIGIT3 = 0x04,
+	MAX2719_CMD_DIGIT4 = 0x05,
+	MAX2719_CMD_DIGIT5 = 0x06,
+	MAX2719_CMD_DIGIT6 = 0x07,
+	MAX2719_CMD_DIGIT7 = 0x08,
+
+	MAX2719_CMD_DECODE_MODE = 0x09,
+	MAX2719_CMD_INTENSITY = 0x0A,
+	MAX2719_CMD_SCAN_LIMIT = 0x0B,
+	MAX2719_CMD_SHUTDOWN = 0x0C,
+	MAX2719_CMD_DISPLAY_TEST = 0x0F,
+} MAX2719_Command;
+
+
+/**
+ * @brief Send a command to a single driver
+ * @param inst : config struct
+ * @param nth  : driver index
+ * @param cmd  : command
+ * @param data : data byte
+ */
+void max2719_cmd(MAX2719_Cfg *inst, uint32_t nth, MAX2719_Command cmd, uint8_t data);
+
+/**
+ * @brief Send command to all drivers, with the same data
+ * @param inst : config struct
+ * @param cmd  : command
+ * @param data : data byte
+ */
+void max2719_cmd_all(MAX2719_Cfg *inst, MAX2719_Command cmd, uint8_t data);
+
+/**
+ * @brief Send command to all drivers, with varying data
+ * @param inst : config struct
+ * @param cmd  : command
+ * @param data : array of data bytes (must be long to cover all drivers)
+ */
+void max2719_cmd_all_data(MAX2719_Cfg *inst, MAX2719_Command cmd, uint8_t *data);
+
+#endif // MAX2719_H
diff --git a/Src/stm32f1xx_it.c b/Src/stm32f1xx_it.c
index 2c8b0aa..55b4251 100644
--- a/Src/stm32f1xx_it.c
+++ b/Src/stm32f1xx_it.c
@@ -31,6 +31,7 @@
   ******************************************************************************
   */
 /* Includes ------------------------------------------------------------------*/
+#include <utils.h>
 #include "stm32f1xx_hal.h"
 #include "stm32f1xx.h"
 #include "stm32f1xx_it.h"
@@ -65,6 +66,7 @@ void NMI_Handler(void)
 void HardFault_Handler(void)
 {
   /* USER CODE BEGIN HardFault_IRQn 0 */
+	uart_print("Hard fault.\n");
 
   /* USER CODE END HardFault_IRQn 0 */
   while (1)
@@ -81,6 +83,7 @@ void HardFault_Handler(void)
 void MemManage_Handler(void)
 {
   /* USER CODE BEGIN MemoryManagement_IRQn 0 */
+	uart_print("MemManage fault.\n");
 
   /* USER CODE END MemoryManagement_IRQn 0 */
   while (1)
@@ -97,6 +100,7 @@ void MemManage_Handler(void)
 void BusFault_Handler(void)
 {
   /* USER CODE BEGIN BusFault_IRQn 0 */
+	uart_print("Bus fault.\n");
 
   /* USER CODE END BusFault_IRQn 0 */
   while (1)
@@ -113,6 +117,7 @@ void BusFault_Handler(void)
 void UsageFault_Handler(void)
 {
   /* USER CODE BEGIN UsageFault_IRQn 0 */
+	uart_print("Usage fault.\n");
 
   /* USER CODE END UsageFault_IRQn 0 */
   while (1)
diff --git a/Src/tim.c b/Src/tim.c
index 2d7f21a..fce6ce9 100644
--- a/Src/tim.c
+++ b/Src/tim.c
@@ -50,7 +50,7 @@ void MX_TIM3_Init(void)
   htim3.Instance = TIM3;
   htim3.Init.Prescaler = 0;
   htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
-  htim3.Init.Period = 1800;
+  htim3.Init.Period = 6000;//1800
   htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
   if (HAL_TIM_OC_Init(&htim3) != HAL_OK)
   {
diff --git a/Src/user_main.c b/Src/user_main.c
index b5600c0..e50ae25 100644
--- a/Src/user_main.c
+++ b/Src/user_main.c
@@ -4,6 +4,7 @@
 
 #include <inttypes.h>
 #include <stm32f1xx_hal_gpio.h>
+#include <dotmatrix.h>
 #include "mxconstants.h"
 #include "stm32f1xx_hal.h"
 #include "utils.h"
@@ -13,23 +14,37 @@
 
 static uint32_t audio_samples[256];
 
+static DotMatrix_Cfg *disp;
+
 void start_DMA() {
-	uart_print("- Starting ADC DMA\n");
+	//uart_print("- Starting ADC DMA\n");
 
-	HAL_ADC_Start_DMA(&hadc1, audio_samples, 256);
+	HAL_ADC_Start_DMA(&hadc1, audio_samples, 32);
 	HAL_TIM_Base_Start(&htim3);
 }
 
 /** This callback is called by HAL after the transfer is complete */
 void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc) {
-	uart_print("- DMA complete.\n");
+//	uart_print("- DMA complete.\n");
 
-	char x[100];
-	sprintf(x, "%"PRIu32"\n", audio_samples[0]);
-	uart_print(x);
+//	char x[100];
+//
+//	for (int i = 0; i < 256; i++) {
+//		sprintf(x, "%"PRIu32" ", audio_samples[i]);
+//		uart_print(x);
+//	}
+//	uart_print("\n");
+
+	dmtx_clear(disp);
+	for (int i = 0; i < 32; i++) {
+		dmtx_set(disp, i, ((audio_samples[i])>>6)-24, 1);
+	}
+	dmtx_show(disp);
 }
 
 void user_main() {
+	uart_print("== USER CODE STARTING ==\n");
+
 	// Leds OFF
 	HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, 1);
 	HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, 1);
@@ -39,13 +54,29 @@ void user_main() {
 	// Enable audio input
 	HAL_GPIO_WritePin(AUDIO_NSTBY_GPIO_Port, AUDIO_NSTBY_Pin, 1);
 
+	DotMatrix_Init disp_init;
+	disp_init.cols = 4;
+	disp_init.rows = 2;
+	disp_init.CS_GPIOx = SPI1_CS_GPIO_Port;
+	disp_init.CS_PINx = SPI1_CS_Pin;
+	disp_init.SPIx = SPI1;
+	disp = dmtx_init(&disp_init);
+
+	dmtx_intensity(disp, 2);
+
+	dmtx_clear(disp);
+	dmtx_show(disp);
+
 	while (1) {
 		// Blink
 		HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
-		HAL_Delay(500);
+		HAL_Delay(50);
 
-		uart_print("Main loop\n");
+		//uart_print("Main loop\n");
 		start_DMA();
+
+		//dmtx_toggle(disp, 31, 15);
+		//dmtx_show(disp);
 	}
 }
 
@@ -64,7 +95,12 @@ void user_Error_Handler() {
    * @retval None
    */
 void user_assert_failed(uint8_t *file, uint32_t line) {
-	uart_print("Assert failed in file ");
+	user_error_file_line("Assert failed", (const char *) file, line);
+}
+
+void user_error_file_line(const char *message, const char *file, uint32_t line) {
+	uart_print(message);
+	uart_print(" in file ");
 	uart_print((char *) file);
 	uart_print(" on line ");