diff --git a/test-app/Makefile b/test-app/Makefile
index c66ab3ef..1b5a2d12 100644
--- a/test-app/Makefile
+++ b/test-app/Makefile
@@ -5,8 +5,8 @@ OBJS:=startup.o main.o timer.o led.o system.o ../src/libwolfboot.o ../hal/$(TARG
 TARGET?=none
 LSCRIPT:=app.ld
 OBJCOPY:=$(CROSS_COMPILE)objcopy
-CFLAGS:=-mcpu=cortex-m3 -mthumb -g -ggdb -Wall -Wno-main -Wstack-usage=200 -ffreestanding -Wno-unused -nostdlib -DPLATFORM_$(TARGET) -I../include
-LDFLAGS:=-T $(LSCRIPT) -Wl,-gc-sections -Wl,-Map=image.map -nostdlib
+CFLAGS:=-mcpu=cortex-m3 -mthumb -g -ggdb -Wall -Wno-main -Wstack-usage=200 -ffreestanding -Wno-unused -DPLATFORM_$(TARGET) -I../include -nostartfiles
+LDFLAGS:=$(CFLAGS) -T $(LSCRIPT) -Wl,-gc-sections -Wl,-Map=image.map
 
 ifeq ($(EXT_FLASH),1)
   CFLAGS+=-DEXT_FLASH=1 -DPART_UPDATE_EXT=1
diff --git a/test-app/app.ld b/test-app/app.ld
index 04c5c6ae..9fd82900 100644
--- a/test-app/app.ld
+++ b/test-app/app.ld
@@ -1,41 +1,43 @@
-MEMORY
-{
-    FLASH (rx) : ORIGIN = 0x00020100, LENGTH = 0x001FF00
-    RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00010000
-}
-
-SECTIONS
-{
-    .text :
-    {
-        _start_text = .;
-        KEEP(*(.isr_vector))
-        *(.text*)
-        *(.rodata*)
-        . = ALIGN(4);
-        _end_text = .;
-    } > FLASH
-
-    _stored_data = .;
-
-    .data : AT (_stored_data)
-    {
-        _start_data = .;
-        KEEP(*(.data*))
-        . = ALIGN(4);
-        _end_data = .;
-    } > RAM
-
-    .bss :
-    {
-        _start_bss = .;
-        *(.bss*)
-        *(COMMON)
-        . = ALIGN(4);
-        _end_bss = .;
-        _end = .;
-    } > RAM
-}
-
-PROVIDE(_start_heap = _end);
-PROVIDE(_end_stack  = ORIGIN(RAM) + LENGTH(RAM));
+MEMORY
+{
+    FLASH (rx) : ORIGIN = 0x00020100, LENGTH = 0x001FF00
+    RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00010000
+}
+
+SECTIONS
+{
+    .text :
+    {
+        _start_text = .;
+        KEEP(*(.isr_vector))
+        *(.init)
+        *(.fini)
+        *(.text*)
+        *(.rodata*)
+        . = ALIGN(4);
+        _end_text = .;
+    } > FLASH
+
+    _stored_data = .;
+
+    .data : AT (_stored_data)
+    {
+        _start_data = .;
+        KEEP(*(.data*))
+        . = ALIGN(4);
+        _end_data = .;
+    } > RAM
+
+    .bss :
+    {
+        _start_bss = .;
+        *(.bss*)
+        *(COMMON)
+        . = ALIGN(4);
+        _end_bss = .;
+        _end = .;
+    } > RAM
+}
+
+PROVIDE(_start_heap = _end);
+PROVIDE(_end_stack  = ORIGIN(RAM) + LENGTH(RAM));
diff --git a/test-app/led.c b/test-app/led.c
index 67018832..bfe66e16 100644
--- a/test-app/led.c
+++ b/test-app/led.c
@@ -22,6 +22,7 @@
  */
 
 #include <stdint.h>
+#include "wolfboot/wolfboot.h"
 
 #define AHB1_CLOCK_ER (*(volatile uint32_t *)(0x40023830))
 #define GPIOD_AHB1_CLOCK_ER (1 << 3)
@@ -59,11 +60,12 @@ void led_pwm_setup(void)
 void boot_led_on(void)
 {
     uint32_t reg;
+    uint32_t pin = LED_BOOT_PIN - 2 * (wolfBoot_current_firmware_version() & 0x01);
     AHB1_CLOCK_ER |= GPIOD_AHB1_CLOCK_ER;
-    reg = GPIOD_MODE & ~(0x03 << (LED_BOOT_PIN * 2));
-    GPIOD_MODE = reg | (1 << (LED_BOOT_PIN * 2));
-    reg = GPIOD_PUPD & ~(0x03 << (LED_BOOT_PIN * 2));
-    GPIOD_PUPD = reg | (1 << (LED_BOOT_PIN * 2));
-    GPIOD_BSRR |= (1 << LED_BOOT_PIN);
+    reg = GPIOD_MODE & ~(0x03 << (pin * 2));
+    GPIOD_MODE = reg | (1 << (pin * 2));
+    reg = GPIOD_PUPD & ~(0x03 << (pin * 2));
+    GPIOD_PUPD = reg | (1 << (pin * 2));
+    GPIOD_BSRR |= (1 << pin);
 }
 
diff --git a/test-app/main.c b/test-app/main.c
index 2edb14fc..48758426 100644
--- a/test-app/main.c
+++ b/test-app/main.c
@@ -23,21 +23,182 @@
 
 #include <stdlib.h>
 #include <stdint.h>
+#include <string.h>
 #include "system.h"
 #include "timer.h"
 #include "led.h"
+#include "hal.h"
 #include "wolfboot/wolfboot.h"
 
 #ifdef PLATFORM_stm32f4
 
+extern int update_started;
+
+#define UART3 (0x40004800)
+
+#define UART3_SR       (*(volatile uint32_t *)(UART3))
+#define UART3_DR       (*(volatile uint32_t *)(UART3 + 0x04))
+#define UART3_BRR      (*(volatile uint32_t *)(UART3 + 0x08))
+#define UART3_CR1      (*(volatile uint32_t *)(UART3 + 0x0c))
+#define UART3_CR2      (*(volatile uint32_t *)(UART3 + 0x10))
+
+#define UART_CR1_UART_ENABLE    (1 << 13)
+#define UART_CR1_SYMBOL_LEN     (1 << 12)
+#define UART_CR1_PARITY_ENABLED (1 << 10)
+#define UART_CR1_PARITY_ODD     (1 << 9)
+#define UART_CR1_TX_ENABLE      (1 << 3)
+#define UART_CR1_RX_ENABLE      (1 << 2)
+#define UART_CR2_STOPBITS       (3 << 12)
+#define UART_SR_TX_EMPTY        (1 << 7)
+#define UART_SR_RX_NOTEMPTY     (1 << 5)
+
+
+#define CLOCK_SPEED (168000000)
+
+#define APB1_CLOCK_ER           (*(volatile uint32_t *)(0x40023840))
+#define UART3_APB1_CLOCK_ER_VAL 	(1 << 18)
+
+#define AHB1_CLOCK_ER (*(volatile uint32_t *)(0x40023830))
+#define GPIOD_AHB1_CLOCK_ER (1 << 3)
+#define GPIOD_BASE 0x40020c00
+#define GPIOD_MODE  (*(volatile uint32_t *)(GPIOD_BASE + 0x00))
+#define GPIOD_AFL   (*(volatile uint32_t *)(GPIOD_BASE + 0x20))
+#define GPIOD_AFH   (*(volatile uint32_t *)(GPIOD_BASE + 0x24))
+#define GPIO_MODE_AF (2)
+#define UART3_PIN_AF 7
+#define UART3_RX_PIN 9
+#define UART3_TX_PIN 8
+
+#define MSGSIZE 16
+#define PAGESIZE (256)
+static uint8_t page[PAGESIZE];
+static const char ERR='!';
+static const char START='*';
+static const char UPDATE='U';
+static const char ACK='#';
+static uint8_t msg[MSGSIZE];
+
+
+void uart_write(const char c)
+{
+    uint32_t reg;
+    do {
+        reg = UART3_SR;
+    } while ((reg & UART_SR_TX_EMPTY) == 0);
+    UART3_DR = c;
+}
+
+static void uart_pins_setup(void)
+{
+    uint32_t reg;
+    AHB1_CLOCK_ER |= GPIOD_AHB1_CLOCK_ER;
+    /* Set mode = AF */
+    reg = GPIOD_MODE & ~ (0x03 << (UART3_RX_PIN * 2));
+    GPIOD_MODE = reg | (2 << (UART3_RX_PIN * 2));
+    reg = GPIOD_MODE & ~ (0x03 << (UART3_TX_PIN * 2));
+    GPIOD_MODE = reg | (2 << (UART3_TX_PIN * 2));
+
+    /* Alternate function: use high pins (8 and 9) */
+    reg = GPIOD_AFH & ~(0xf << ((UART3_TX_PIN - 8) * 4));
+    GPIOD_AFH = reg | (UART3_PIN_AF << ((UART3_TX_PIN - 8) * 4));
+    reg = GPIOD_AFH & ~(0xf << ((UART3_RX_PIN - 8) * 4));
+    GPIOD_AFH = reg | (UART3_PIN_AF << ((UART3_RX_PIN - 8) * 4));
+}
+
+int uart_setup(uint32_t bitrate, uint8_t data, char parity, uint8_t stop)
+{
+    uint32_t reg;
+    /* Enable pins and configure for AF7 */
+    uart_pins_setup();
+    /* Turn on the device */
+    APB1_CLOCK_ER |= UART3_APB1_CLOCK_ER_VAL;
+
+    /* Configure for TX + RX */
+    UART3_CR1 |= (UART_CR1_TX_ENABLE | UART_CR1_RX_ENABLE);
+
+    /* Configure clock */
+    UART3_BRR =  CLOCK_SPEED / bitrate;
+
+    /* Configure data bits */
+    if (data == 8)
+        UART3_CR1 &= ~UART_CR1_SYMBOL_LEN;
+    else
+        UART3_CR1 |= UART_CR1_SYMBOL_LEN;
+
+    /* Configure parity */
+    switch (parity) {
+        case 'O':
+            UART3_CR1 |= UART_CR1_PARITY_ODD;
+            /* fall through to enable parity */
+        case 'E':
+            UART3_CR1 |= UART_CR1_PARITY_ENABLED;
+            break;
+        default:
+            UART3_CR1 &= ~(UART_CR1_PARITY_ENABLED | UART_CR1_PARITY_ODD);
+    }
+    /* Set stop bits */
+    reg = UART3_CR2 & ~UART_CR2_STOPBITS;
+    if (stop > 1)
+        UART3_CR2 = reg & (2 << 12);
+    else
+        UART3_CR2 = reg;
+
+    /* Turn on uart */
+    UART3_CR1 |= UART_CR1_UART_ENABLE;
+
+    return 0;
+}
+
+char uart_read(void)
+{
+    char c;
+    volatile uint32_t reg;
+    do {
+        reg = UART3_SR;
+    } while ((reg & UART_SR_RX_NOTEMPTY) == 0);
+    c = (char)(UART3_DR & 0xff);
+    return c;
+}
+
+static void ack(uint32_t _off)
+{
+    uint8_t *off = (uint8_t *)(&_off);
+    int i;
+    uart_write(ACK);
+    for (i = 0; i < 4; i++) {
+        uart_write(off[i]);
+    }
+}
+
+static int check(uint8_t *pkt, int size)
+{
+    int i;
+    uint16_t c = 0;
+    uint16_t c_rx = *((uint16_t *)(pkt + 2));
+    uint16_t *p = (uint16_t *)(pkt + 4);
+    for (i = 0; i < ((size - 4) >> 1); i++)
+        c += p[i];
+    if (c == c_rx)
+        return 0;
+    return -1;
+}
+
 void main(void) {
-    uint32_t version;
+    uint32_t tlen = 0;
+    volatile uint32_t recv_seq;
+    uint32_t r_total = 0;
+    uint32_t tot_len = 0;
+    uint32_t next_seq = 0;
+    uint32_t version = 0;
+    uint8_t *v_array = (uint8_t *)&version;
+    int i;
+    memset(page, 0xFF, PAGESIZE);
     boot_led_on();
     flash_set_waitstates();
     clock_config();
     led_pwm_setup();
     pwm_init(CPU_FREQ, 0);
-    /* Dim the led by altering the PWM duty-cicle 
+    /* Dim the led by altering the PWM duty-cicle
      * in isr_tim2 (timer.c)
      *
      * Every 50ms, the duty cycle of the PWM connected
@@ -45,18 +206,80 @@ void main(void) {
      * effect.
      */
     timer_init(CPU_FREQ, 1, 50);
-    version = wolfBoot_current_firmware_version();
-    if (version & 0x01) {
-        /* Odd version: unstable, trigger update */
-        if (wolfBoot_update_firmware_version() != 0)
-            wolfBoot_update_trigger();
-    } else {
-        /* Even version, stabilise */
-        wolfBoot_success();
-    }
+    uart_setup(115200, 8, 'N', 1);
+    memset(page, 0xFF, PAGESIZE);
     asm volatile ("cpsie i");
+    /* Initiate update */
+
+    //wolfBoot_success();
+
+    hal_flash_unlock();
+    uart_write(START);
+    while (1) {
+        r_total = 0;
+        do {
+            while(r_total < 2) {
+                msg[r_total++] = uart_read();
+                if ((r_total == 2) && ((msg[0] != 0xA5) || msg[1] != 0x5A)) {
+                    r_total = 0;
+                    continue;
+                }
+            }
+            msg[r_total++] = uart_read();
+            if ((tot_len == 0) && r_total == 2 + sizeof(uint32_t))
+                break;
+            if ((r_total > 8)  && (tot_len <= ((r_total - 8) + next_seq)))
+                break;
+        } while (r_total < MSGSIZE);
+        if (tot_len == 0)  {
+            tlen = msg[2] + (msg[3] << 8) + (msg[4] << 16) + (msg[5] << 24);
+            if (tlen > WOLFBOOT_PARTITION_SIZE - 8) {
+                uart_write(ERR);
+                uart_write(ERR);
+                uart_write(ERR);
+                uart_write(ERR);
+                uart_write(START);
+                recv_seq = 0;
+                tot_len = 0;
+                update_started = 1;
+                continue;
+            }
+            tot_len = tlen;
+            ack(0);
+            continue;
+        }
+        if (check(msg, r_total) < 0) {
+            ack(next_seq);
+            continue;
+        }
+        recv_seq = msg[4] + (msg[5] << 8) + (msg[6] << 16) + (msg[7] << 24);
+        if (recv_seq == next_seq)
+        {
+            int psize = r_total - 8;
+            int page_idx = recv_seq % PAGESIZE;
+            memcpy(&page[recv_seq % PAGESIZE], msg + 8, psize);
+            page_idx += psize;
+            if ((page_idx == PAGESIZE) || (next_seq + psize >= tot_len)) {
+                uint32_t dst = (WOLFBOOT_PARTITION_UPDATE_ADDRESS + recv_seq + psize) - page_idx;
+                if ((dst % WOLFBOOT_SECTOR_SIZE) == 0) {
+                    hal_flash_erase(dst, WOLFBOOT_SECTOR_SIZE);
+                }
+                hal_flash_write(dst, page, PAGESIZE);
+                memset(page, 0xFF, PAGESIZE);
+            }
+            next_seq += psize;
+        }
+        ack(next_seq);
+        if (next_seq >= tot_len) {
+            /* Update complete */
+            wolfBoot_update_trigger();
+            hal_flash_lock();
+            break;
+        }
+    }
+    /* Wait for reboot */
     while(1)
-        WFI();
+        ;
 }
 #endif
 
diff --git a/test-app/timer.c b/test-app/timer.c
index f1517bb1..7f810390 100644
--- a/test-app/timer.c
+++ b/test-app/timer.c
@@ -84,7 +84,7 @@ int pwm_init(uint32_t clock, uint32_t threshold)
     lvl = (val * threshold) / 100;
     if (lvl != 0)
         lvl--;
-    
+
     APB1_CLOCK_RST |= TIM4_APB1_CLOCK_ER_VAL;
     __asm__ volatile ("dmb");
     APB1_CLOCK_RST &= ~TIM4_APB1_CLOCK_ER_VAL;
@@ -145,7 +145,10 @@ int timer_init(uint32_t clock, uint32_t prescaler, uint32_t interval_ms)
     return 0;
 }
 
-void isr_tim2(void) 
+int update_started = 0;
+extern void uart_write(char c);
+
+void isr_tim2(void)
 {
     static volatile uint32_t tim2_ticks = 0;
     TIM2_SR &= ~TIM_SR_UIF;
@@ -157,6 +160,9 @@ void isr_tim2(void)
         pwm_init(master_clock, 10 * (16 - tim2_ticks));
     else
         pwm_init(master_clock, 10 * tim2_ticks);
+
+    if (!update_started)
+        uart_write('*');
 }