Fix serial

14 files changed, 447 insertions, 42 deletions

diff --git a/.gitmodules b/.gitmodules
index 755dc2f..9da9307 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -19,3 +19,6 @@
 [submodule "controller/fw/crypto-algorithms"]
 	path = controller/fw/crypto-algorithms
 	url = https://github.com/B-Con/crypto-algorithms
+[submodule "controller/fw/tinyprintf"]
+	path = controller/fw/tinyprintf
+	url = https://github.com/cjlano/tinyprintf
diff --git a/controller/fw/Makefile b/controller/fw/Makefile
index 0fea8ae..50d162d 100644
--- a/controller/fw/Makefile
+++ b/controller/fw/Makefile
@@ -42,8 +42,18 @@ PRESIG_KEYFILE			?= presig_test_key.secret
 # Sources
 ########################################################################################################################
 
-C_SOURCES		:= src/main.c src/mspdebug_wrapper.c src/spi_flash.c src/freq_meas.c src/dsss_demod.c src/adc.c \
-					src/protocol.c
+C_SOURCES		:= src/main.c
+C_SOURCES		+= src/mspdebug_wrapper.c
+C_SOURCES		+= src/spi_flash.c
+C_SOURCES		+= src/freq_meas.c
+C_SOURCES		+= src/dsss_demod.c
+C_SOURCES		+= src/adc.c
+C_SOURCES		+= src/protocol.c
+C_SOURCES		+= src/serial.c
+C_SOURCES		+= src/con_usart.c
+C_SOURCES		+= src/dma_util.c
+C_SOURCES		+= tinyprintf/tinyprintf.c
+
 C_SOURCES		+= $(MSPDEBUG_DIR)/drivers/jtaglib.c
 
 CMSIS_SOURCES		+= $(CMSIS_DIR)/CMSIS/DSP/Source/TransformFunctions/arm_rfft_fast_init_f32.c
@@ -121,6 +131,7 @@ SYSTEM_FLAGS	?= -nostdlib -ffreestanding -nostartfiles
 COMMON_CFLAGS		+= -Imspdebug/util -Imspdebug/drivers -Ilevmarq
 COMMON_CFLAGS		+= -I$(CMSIS_DIR_ABS)/CMSIS/DSP/Include -I$(CMSIS_DIR_ABS)/CMSIS/Core/Include 
 CFLAGS				+= -I$(abspath musl_include_shims)
+CFLAGS				+= -Itinyprintf
 COMMON_CFLAGS		+= -I$(BUILDDIR) -Isrc -Itinyaes
 CFLAGS				+= -I$(CUBE_DIR)/Drivers/CMSIS/Device/ST/STM32F4xx/Include
 
diff --git a/controller/fw/src/adc.c b/controller/fw/src/adc.c
index 74f0aa9..81f5ac1 100644
--- a/controller/fw/src/adc.c
+++ b/controller/fw/src/adc.c
@@ -1,8 +1,7 @@
 
+#include <assert.h>
 #include <string.h>
-
-#include <stm32f407xx.h>
-#include <stm32f4_isr.h>
+#include <stdint.h>
 
 #include "adc.h"
 #include "sr_global.h"
@@ -58,9 +57,10 @@ void adc_init() {
     TIM1->CR2 = (2<<TIM_CR2_MMS_Pos); /* Enable update event on TRGO to provide a 1ms reference to rest of system */
     TIM1->CCMR1 = (6<<TIM_CCMR1_OC1M_Pos) | (0<<TIM_CCMR1_CC1S_Pos);
     TIM1->CCER = TIM_CCER_CC1E;
-    TIM1->PSC = 84-1; /* 1us ticks @ f_APB2=84MHz */
-    TIM1->ARR = 1000-1; /* 1ms period */
-    TIM1->CCR1 = 500-1;
+    assert(apb2_timer_speed%1000000 == 0);
+    TIM1->PSC = 1000-1;
+    TIM1->ARR = (apb2_timer_speed/1000000)-1; /* 1ms period */
+    TIM1->CCR1 = 1;
     TIM1->BDTR = TIM_BDTR_MOE;
     
     /* DEBUG */
@@ -85,14 +85,12 @@ void TIM1_CC_IRQHandler(void) {
 
 void DMA2_Stream0_IRQHandler(void) {
     uint8_t isr = (DMA2->LISR >> DMA_LISR_FEIF0_Pos) & 0x3f;
-
-    GPIOA->ODR ^= 1<<7;
-    GPIOA->BSRR = 1<<10;
+    GPIOA->BSRR = 1<<11;
 
     if (isr & DMA_LISR_TCIF0) { /* Transfer complete */
         /* Check we're done processing the old buffer */
         if (adc_fft_buf_ready_idx != -1) { /* FIXME DEBUG */
-            GPIOA->BSRR = 1<<10<<16;
+            GPIOA->BSRR = 1<<11<<16;
             /* clear all flags */
             adc_dma->LIFCR = isr<<DMA_LISR_FEIF0_Pos;
             return;
@@ -110,7 +108,7 @@ void DMA2_Stream0_IRQHandler(void) {
     if (isr & DMA_LISR_TEIF0) /* Transfer error */
         panic();
 
-    GPIOA->BSRR = 1<<10<<16;
+    GPIOA->BSRR = 1<<11<<16;
     /* clear all flags */
     adc_dma->LIFCR = isr<<DMA_LISR_FEIF0_Pos;
 }
diff --git a/controller/fw/src/con_usart.c b/controller/fw/src/con_usart.c
new file mode 100644
index 0000000..f80fa79
--- /dev/null
+++ b/controller/fw/src/con_usart.c
@@ -0,0 +1,33 @@
+
+#include <stm32f4_isr.h>
+#include "con_usart.h"
+
+volatile struct usart_desc con_usart = {
+    .le_usart = USART1,
+    .le_usart_irqn = USART1_IRQn,
+    .tx_dmas = DMA2_Stream7,
+    .tx_dma_sn = 7,
+    .tx_dma_ch = 4,
+    .tx_dma = DMA2,
+    .tx_dma_irqn = DMA2_Stream7_IRQn,
+};
+
+void con_usart_init() {
+    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN | RCC_AHB1ENR_DMA2EN;
+    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;
+
+    /* GPIO config: A9 (TX), A10 (RX) */
+    GPIOA->MODER &= ~GPIO_MODER_MODER9_Msk & ~GPIO_MODER_MODER10_Msk;
+    GPIOA->MODER |= (2<<GPIO_MODER_MODER9_Pos) | (2<<GPIO_MODER_MODER10_Pos);
+    GPIOA->OSPEEDR &= ~GPIO_OSPEEDR_OSPEED9_Msk & ~GPIO_OSPEEDR_OSPEED10_Msk;
+    GPIOA->OSPEEDR |= (2<<GPIO_OSPEEDR_OSPEED9_Pos) | (2<<GPIO_OSPEEDR_OSPEED10_Pos);
+    GPIOA->AFR[1] &= ~GPIO_AFRH_AFSEL9_Msk & ~GPIO_AFRH_AFSEL10_Msk;
+    GPIOA->AFR[1] |= (7<<GPIO_AFRH_AFSEL9_Pos) | (7<<GPIO_AFRH_AFSEL10_Pos);
+
+    usart_dma_init(&con_usart, CON_USART_BAUDRATE);
+}
+
+void DMA2_Stream7_IRQHandler(void) {
+    usart_dma_stream_irq(&con_usart);
+}
+
diff --git a/controller/fw/src/con_usart.h b/controller/fw/src/con_usart.h
new file mode 100644
index 0000000..a1ad963
--- /dev/null
+++ b/controller/fw/src/con_usart.h
@@ -0,0 +1,16 @@
+#ifndef __CON_USART_H__
+#define __CON_USART_H__
+
+#include "serial.h"
+
+extern volatile struct usart_desc con_usart;
+
+#define con_printf(...) usart_printf(&con_usart, __VA_ARGS__)
+
+#ifndef CON_USART_BAUDRATE
+#define CON_USART_BAUDRATE 115200
+#endif
+
+void con_usart_init(void);
+
+#endif /* __CON_USART_H__ */
diff --git a/controller/fw/src/dma_util.c b/controller/fw/src/dma_util.c
new file mode 100644
index 0000000..48de215
--- /dev/null
+++ b/controller/fw/src/dma_util.c
@@ -0,0 +1,46 @@
+
+#include <assert.h>
+
+#include "dma_util.h"
+
+uint8_t dma_get_isr_and_clear(DMA_TypeDef *dma, int ch) {
+    uint8_t isr_val;
+    switch(ch) {
+        case 0:
+            isr_val = dma->LISR & 0x3f; 
+            dma->LIFCR = isr_val;
+            return isr_val;
+        case 1:
+            isr_val = dma->LISR>>6 & 0x3f; 
+            dma->LIFCR = isr_val<<6;
+            return isr_val;
+        case 2:
+            isr_val = dma->LISR>>16 & 0x3f; 
+            dma->LIFCR = isr_val<<16;
+            return isr_val;
+        case 3:
+            isr_val = dma->LISR>>6>>16 & 0x3f; 
+            dma->LIFCR = isr_val<<6<<16;
+            return isr_val;
+        case 4:
+            isr_val = dma->HISR & 0x3f; 
+            dma->HIFCR = isr_val;
+            return isr_val;
+        case 5:
+            isr_val = dma->HISR>>6 & 0x3f; 
+            dma->HIFCR = isr_val<<6;
+            return isr_val;
+        case 6:
+            isr_val = dma->HISR>>16 & 0x3f; 
+            dma->HIFCR = isr_val<<16;
+            return isr_val;
+        case 7:
+            isr_val = dma->HISR>>6>>16 & 0x3f; 
+            dma->HIFCR = isr_val<<6<<16;
+            return isr_val;
+        default:
+            assert(0);
+            return 0;
+    }
+}
+
diff --git a/controller/fw/src/dma_util.h b/controller/fw/src/dma_util.h
new file mode 100644
index 0000000..5ea2676
--- /dev/null
+++ b/controller/fw/src/dma_util.h
@@ -0,0 +1,10 @@
+#ifndef __DMA_UTIL_H__
+#define __DMA_UTIL_H__
+
+#include <stdint.h>
+
+#include "sr_global.h"
+
+uint8_t dma_get_isr_and_clear(DMA_TypeDef *dma, int ch);
+
+#endif /* __DMA_UTIL_H__ */
diff --git a/controller/fw/src/freq_meas.c b/controller/fw/src/freq_meas.c
index 020e12d..6b9b54e 100644
--- a/controller/fw/src/freq_meas.c
+++ b/controller/fw/src/freq_meas.c
@@ -136,7 +136,13 @@ int adc_buf_measure_freq(uint16_t adc_buf[FMEAS_FFT_LEN], float *out) {
 
     DEBUG_PRINT("done.");
     */
-    *out = (par[1] + first_bin) * binsize_hz;
+    float res = (par[1] + first_bin) * binsize_hz;
+    if (res < 5 || res > 150) {
+        *out = NAN;
+        return -1;
+    }
+    
+    *out = res;
     return 0;
 }
 
diff --git a/controller/fw/src/main.c b/controller/fw/src/main.c
index fa5d50b..b100b16 100644
--- a/controller/fw/src/main.c
+++ b/controller/fw/src/main.c
@@ -6,15 +6,25 @@
 #include <math.h>
 
 #include <stm32f407xx.h>
+#include <stm32f4_isr.h>
 
 #include "sr_global.h"
 #include "adc.h"
 #include "spi_flash.h"
 #include "freq_meas.h"
 #include "dsss_demod.h"
+#include "con_usart.h"
 
 static struct spi_flash_if spif;
 
+unsigned int sysclk_speed = 0;
+unsigned int apb1_speed = 0;
+unsigned int apb2_speed = 0;
+unsigned int auxclk_speed = 0;
+unsigned int apb1_timer_speed = 0;
+unsigned int apb2_timer_speed = 0;
+
+struct leds leds;
 
 void __libc_init_array(void) { /* we don't need this. */ }
 void __assert_func (unused_a const char *file, unused_a int line, unused_a const char *function, unused_a const char *expr) {
@@ -24,14 +34,14 @@ void __assert_func (unused_a const char *file, unused_a int line, unused_a const
 
 static void clock_setup(void)
 {
-    /* 8MHz HSE clock as PLL source.
-     * 
-     * Divide by 8 -> 1 MHz */
+    /* 8MHz HSE clock as PLL source. */
+#define HSE_SPEED 8000000
+    /* Divide by 8 -> 1 MHz */
 #define PLL_M 8
     /* Multiply by 336 -> 336 MHz VCO frequency */
 #define PLL_N 336
     /* Divide by 4 -> 84 MHz (max freq for our chip) */
-#define PLL_P 4
+#define PLL_P 2
     /* Aux clock for USB OTG, SDIO, RNG: divide VCO frequency (336 MHz) by 7 -> 48 MHz (required by USB OTG) */
 #define PLL_Q 7
 
@@ -54,10 +64,10 @@ static void clock_setup(void)
 
     /* set AHB prescaler to /1 (CFGR:bits 7:4) */
     RCC->CFGR |= (0 << RCC_CFGR_HPRE_Pos);
-    /* set ABP1 prescaler to 2 -> 42MHz */
-    RCC->CFGR |= (4 << RCC_CFGR_PPRE1_Pos);
-    /* set ABP2 prescaler to 1 -> 84MHz */
-    RCC->CFGR |= (0 << RCC_CFGR_PPRE2_Pos);
+    /* set ABP1 prescaler to 4 -> 42MHz */
+    RCC->CFGR |= (5 << RCC_CFGR_PPRE1_Pos);
+    /* set ABP2 prescaler to 2 -> 84MHz */
+    RCC->CFGR |= (4 << RCC_CFGR_PPRE2_Pos);
 
     if (RCC->CR & RCC_CR_PLLON)
         asm volatile ("bkpt");
@@ -79,6 +89,13 @@ static void clock_setup(void)
         | RCC_PLLCFGR_PLLSRC; /* select HSE as PLL source */
     RCC->CR |= RCC_CR_PLLON;
 
+    sysclk_speed = HSE_SPEED / PLL_M * PLL_N / PLL_P;
+    auxclk_speed = HSE_SPEED / PLL_M * PLL_N / PLL_Q;
+    apb1_speed = sysclk_speed / 4;
+    apb1_timer_speed = apb1_speed * 2;
+    apb2_speed = sysclk_speed / 2;
+    apb2_timer_speed = apb2_speed * 2;
+
     /* Wait for main PLL */
     while(!(RCC->CR & RCC_CR_PLLRDY))
         ;
@@ -170,7 +187,7 @@ int main(void)
     GPIOC->MODER &= ~GPIO_MODER_MODER9_Msk;
     GPIOC->MODER |= (2<<GPIO_MODER_MODER9_Pos);
     GPIOC->AFR[1] &= ~GPIO_AFRH_AFSEL9_Msk;
-    GPIOC->OSPEEDR |= (3<<GPIO_OSPEEDR_OSPEED9_Pos); /* SCK */
+    GPIOC->OSPEEDR |= (3<<GPIO_OSPEEDR_OSPEED9_Pos);
     RCC->CFGR |= (6<<RCC_CFGR_MCO2PRE_Pos) | (3<<RCC_CFGR_MCO2_Pos);
 #endif
 
@@ -179,6 +196,9 @@ int main(void)
     }
 
     clock_setup();
+    con_usart_init();
+    con_printf("\033[2J\033[HBooting...\r\n");
+
     led_setup();
     spi_flash_setup();
     adc_init();
@@ -190,30 +210,38 @@ int main(void)
     GPIOA->AFR[1] &= ~GPIO_AFRH_AFSEL8_Msk;
     GPIOA->AFR[1] |= 1<<GPIO_AFRH_AFSEL8_Pos;
 
-    GPIOA->MODER |= (1<<GPIO_MODER_MODER9_Pos) | (1<<GPIO_MODER_MODER10_Pos) | (1<<GPIO_MODER_MODER11_Pos) |
-        (1<<GPIO_MODER_MODER12_Pos) | (1<<GPIO_MODER_MODER15_Pos);
+    GPIOA->MODER |= (1<<GPIO_MODER_MODER11_Pos) | (1<<GPIO_MODER_MODER12_Pos) | (1<<GPIO_MODER_MODER15_Pos);
 #endif
 
+    con_printf("Booted.\r\n");
     while (23) {
         if (adc_fft_buf_ready_idx != -1) {
-            GPIOA->BSRR = 1<<9;
+            GPIOA->BSRR = 1<<11;
             adc_fft_buf_ready_idx = !adc_fft_buf_ready_idx; /* DEBUG */
             memcpy(adc_fft_buf[!adc_fft_buf_ready_idx], adc_fft_buf[adc_fft_buf_ready_idx] + FMEAS_FFT_LEN/2, sizeof(adc_fft_buf[0][0]) * FMEAS_FFT_LEN/2);
-            GPIOA->BSRR = 1<<9<<16;
-            GPIOA->BSRR = 1<<11;
+            GPIOA->BSRR = 1<<11<<16;
 
+            GPIOA->BSRR = 1<<11;
             float out;
             if (adc_buf_measure_freq(adc_fft_buf[adc_fft_buf_ready_idx], &out)) {
+                con_printf("%012d: measurement error\r\n", freq_sample_ts);
                 measurement_errors++;
+                GPIOA->BSRR = 1<<7;
                 debug_last_freq = NAN;
 
             } else {
                 debug_last_freq = out;
-
-                /*
+                con_printf("%012d: %2d.%03d Hz\r\n", freq_sample_ts, (int)out, (int)(out * 1000) % 1000);
+                /* frequency ok led */
+                if (48 < out && out < 52)
+                    GPIOA->BSRR = 1<<7<<16;
+                else
+                    GPIOA->BSRR = 1<<7;
+
+                GPIOA->BSRR = 1<<12;
                 dsss_demod_init(&demod_state);
                 dsss_demod_step(&demod_state, out, freq_sample_ts);
-                */
+                GPIOA->BSRR = 1<<12<<16;
             }
             GPIOA->BSRR = 1<<11<<16;
 
@@ -226,38 +254,38 @@ int main(void)
 }
 
 void NMI_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #1");
 }
 
 void HardFault_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #2");
 }
 
 void MemManage_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #3");
 }
 
 void BusFault_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #4");
 }
 
 void UsageFault_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #5");
 }
 
 void SVC_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #6");
 }
 
 void DebugMon_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #7");
 }
 
 void PendSV_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #8");
 }
 
 void SysTick_Handler(void) {
-    asm volatile ("bkpt");
+    asm volatile ("bkpt #9");
 }
 
diff --git a/controller/fw/src/protocol.c b/controller/fw/src/protocol.c
index 17020bd..bbee5ef 100644
--- a/controller/fw/src/protocol.c
+++ b/controller/fw/src/protocol.c
@@ -1,7 +1,13 @@
 
 #include "sr_global.h"
 #include "dsss_demod.h"
+#include "con_usart.h"
 
-void handle_dsss_received(uint8_t unused_a data[static TRANSMISSION_SYMBOLS]) {
-    asm volatile ("bkpt");
+void handle_dsss_received(uint8_t data[static TRANSMISSION_SYMBOLS]) {
+    con_printf("DSSS data received: ");
+    for (int i=0; i<TRANSMISSION_SYMBOLS; i++) {
+        int x = (data[i]>>1) * (data[i]&1 ? 1 : -1);
+        con_printf("%3d ", x);
+    }
+    con_printf("\r\n");
 }
diff --git a/controller/fw/src/serial.c b/controller/fw/src/serial.c
new file mode 100644
index 0000000..71e1868
--- /dev/null
+++ b/controller/fw/src/serial.c
@@ -0,0 +1,153 @@
+#include <string.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+#include "dma_util.h"
+#include "sr_global.h"
+#include "serial.h"
+
+#include <tinyprintf.h>
+
+static void usart_schedule_dma(volatile struct usart_desc *us);
+static void usart_dma_reset(volatile struct usart_desc *us);
+static void usart_putc_nonblocking_tpf(void *us, char c);
+
+void usart_dma_reset(volatile struct usart_desc *us) {
+    us->tx_buf.xfr_start = -1;
+    us->tx_buf.xfr_end = 0;
+    us->tx_buf.wr_pos = 0;
+    us->tx_buf.wr_idx = 0;
+    us->tx_buf.xfr_next = 0;
+    us->tx_buf.wraparound = false;
+
+    for (size_t i=0; i<ARRAY_LENGTH(us->tx_buf.chunk_end); i++)
+        us->tx_buf.chunk_end[i] = -1;
+}
+
+void usart_dma_init(volatile struct usart_desc *us, unsigned int baudrate) {
+    usart_dma_reset(us);
+
+    /* Configure DMA 1 Channel 2 to handle uart transmission */
+    us->tx_dmas->PAR = (uint32_t)&(us->le_usart->DR);
+    us->tx_dmas->CR =
+          (us->tx_dma_ch<<DMA_SxCR_CHSEL_Pos)
+        | (0<<DMA_SxCR_PL_Pos)
+        | (1<<DMA_SxCR_DIR_Pos)
+        | (0<<DMA_SxCR_MSIZE_Pos) /* 8 bit */
+        | (0<<DMA_SxCR_PSIZE_Pos) /* 8 bit */
+        | DMA_SxCR_MINC
+        | DMA_SxCR_TCIE; /* Enable transfer complete interrupt. */
+
+    /* triggered on transfer completion. We use this to process the ADC data */
+    NVIC_EnableIRQ(us->tx_dma_irqn);
+    NVIC_SetPriority(us->tx_dma_irqn, 30);
+
+    us->le_usart->CR1 = USART_CR1_TE;
+    /* Set divider for 115.2kBd @48MHz system clock. */
+    us->le_usart->BRR = apb2_speed * 16 / baudrate / 16; /* 250kBd */
+    us->le_usart->CR3 |= USART_CR3_DMAT; /* TX DMA enable */
+
+    /* And... go! */
+    us->le_usart->CR1 |= USART_CR1_UE;
+}
+
+void usart_schedule_dma(volatile struct usart_desc *us) {
+    volatile struct dma_tx_buf *buf = &us->tx_buf;
+
+    ssize_t xfr_start, xfr_end, xfr_len;
+    if (buf->wraparound) {
+        buf->wraparound = false;
+        xfr_start = 0;
+        xfr_len = buf->xfr_end;
+        xfr_end = buf->xfr_end;
+
+    } else {
+        if (buf->chunk_end[buf->xfr_next] == -1)
+            return; /* Nothing to trasnmit */
+
+        xfr_start = buf->xfr_end;
+        xfr_end = buf->chunk_end[buf->xfr_next];
+        buf->chunk_end[buf->xfr_next] = -1;
+        buf->xfr_next = (buf->xfr_next + 1) % ARRAY_LENGTH(buf->chunk_end);
+
+        if (xfr_end > xfr_start) { /* no wraparound */
+            xfr_len = xfr_end - xfr_start;
+
+        } else { /* wraparound */
+            if (xfr_end != 0)
+                buf->wraparound = true;
+            xfr_len = sizeof(us->data) - xfr_start;
+        }
+    }
+
+    buf->xfr_start = xfr_start;
+    buf->xfr_end = xfr_end;
+
+    us->comm_led = 100;
+
+    /* initiate transmission of new buffer */
+    us->tx_dmas->M0AR = (uint32_t)(us->data + xfr_start);
+    us->tx_dmas->NDTR = xfr_len;
+    us->tx_dmas->CR |= DMA_SxCR_EN;
+}
+
+void usart_dma_stream_irq(volatile struct usart_desc *us) {
+    uint8_t iflags = dma_get_isr_and_clear(us->tx_dma, us->tx_dma_sn);
+
+    if (iflags & DMA_LISR_TCIF0) { /* Transfer complete */
+        us->tx_dmas->CR &= ~DMA_SxCR_EN;
+        //if (us->tx_buf.wraparound)
+        usart_schedule_dma(us);
+    }
+
+    if (iflags & DMA_LISR_FEIF0)
+        us->tx_errors++;
+}
+
+int usart_putc_nonblocking(volatile struct usart_desc *us, char c) {
+    volatile struct dma_tx_buf *buf = &us->tx_buf;
+
+    if (buf->wr_pos == buf->xfr_start) {
+        us->tx_byte_overruns++;
+        return -EBUSY;
+    }
+
+    buf->data[buf->wr_pos] = c;
+    buf->wr_pos = (buf->wr_pos + 1) % sizeof(us->data);
+    return 0;
+}
+
+void usart_putc_nonblocking_tpf(void *us, char c) {
+    usart_putc_nonblocking((struct usart_desc *)us, c);
+}
+
+
+int usart_send_chunk_nonblocking(volatile struct usart_desc *us, const char *chunk, size_t chunk_len) {
+    for (size_t i=0; i<chunk_len; i++)
+        usart_putc_nonblocking(us, chunk[i]);
+
+    return usart_flush(us);
+}
+
+int usart_flush(volatile struct usart_desc *us) {
+    /* Find a free slot for this chunk */
+    if (us->tx_buf.chunk_end[us->tx_buf.wr_idx] != -1) {
+        us->tx_chunk_overruns++;
+        return -EBUSY;
+    }
+
+    us->tx_buf.chunk_end[us->tx_buf.wr_idx] = us->tx_buf.wr_pos;
+    us->tx_buf.wr_idx = (us->tx_buf.wr_idx + 1) % ARRAY_LENGTH(us->tx_buf.chunk_end);
+
+    if (!(us->tx_dmas->CR & DMA_SxCR_EN))
+        usart_schedule_dma(us);
+    return 0;
+}
+
+int usart_printf(volatile struct usart_desc *us, char *fmt, ...) {
+    va_list va;
+    va_start(va, fmt);
+    tfp_format((void *)us, usart_putc_nonblocking_tpf, fmt, va);
+    return usart_flush(us);
+}
+
diff --git a/controller/fw/src/serial.h b/controller/fw/src/serial.h
new file mode 100644
index 0000000..02f6f5d
--- /dev/null
+++ b/controller/fw/src/serial.h
@@ -0,0 +1,82 @@
+/*

+ * This file is part of the libusbhost library

+ * hosted at http://github.com/libusbhost/libusbhost

+ *

+ * Copyright (C) 2015 Amir Hammad <amir.hammad@hotmail.com>

+ *

+ *

+ * libusbhost is free software: you can redistribute it and/or modify

+ * it under the terms of the GNU Lesser General Public License as published by

+ * the Free Software Foundation, either version 3 of the License, or

+ * (at your option) any later version.

+ *

+ * This library is distributed in the hope that it will be useful,

+ * but WITHOUT ANY WARRANTY; without even the implied warranty of

+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+ * GNU Lesser General Public License for more details.

+ *

+ * You should have received a copy of the GNU Lesser General Public License

+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.

+ *

+ */

+

+#ifndef __SERIAL_H__

+#define __SERIAL_H__

+

+#include <stdint.h>

+#include <stddef.h>

+#include <stdarg.h>

+#include <errno.h>

+#include <stdbool.h>

+

+#include "sr_global.h"

+

+struct dma_tx_buf {

+    /* The following fields are accessed only from DMA ISR */

+    ssize_t xfr_start; /* Start index of running DMA transfer */

+    ssize_t xfr_end; /* End index of running DMA transfer plus one */

+    bool wraparound;

+    ssize_t xfr_next;

+

+    /* The following fields are written only from non-interrupt code */

+    ssize_t wr_pos; /* Next index to be written */

+    ssize_t wr_idx;

+    ssize_t chunk_end[8];

+

+/* Make GCC shut up about the zero-size array member. */

+#pragma GCC diagnostic push

+#pragma GCC diagnostic ignored "-Wpedantic"

+    /* Written outside ISR by usart_send_chunk_nonblocking, read via DMA */

+    uint8_t data[0];

+#pragma GCC diagnostic pop

+};

+

+struct usart_desc {

+    struct dma_tx_buf tx_buf;

+    uint8_t data[512];

+

+    uint32_t tx_chunk_overruns, tx_byte_overruns;

+    uint32_t tx_errors;

+

+    volatile uint8_t rx_buf[32];

+

+    int comm_led;

+

+    USART_TypeDef *le_usart;

+    int le_usart_irqn;

+    DMA_Stream_TypeDef *tx_dmas;

+    int tx_dma_sn;

+    int tx_dma_ch;

+    DMA_TypeDef *tx_dma;

+    int tx_dma_irqn;

+};

+

+void usart_dma_init(volatile struct usart_desc *us, unsigned int baudrate);

+int usart_send_chunk_nonblocking(volatile struct usart_desc *us, const char *chunk, size_t chunk_len);

+int usart_putc_nonblocking(volatile struct usart_desc *us, char c);

+

+void usart_dma_stream_irq(volatile struct usart_desc *us);

+int usart_flush(volatile struct usart_desc *us);

+int usart_printf(volatile struct usart_desc *us, char *fmt, ...);

+

+#endif // __SERIAL_H__

diff --git a/controller/fw/src/sr_global.h b/controller/fw/src/sr_global.h
index ac77359..451cce0 100644
--- a/controller/fw/src/sr_global.h
+++ b/controller/fw/src/sr_global.h
@@ -2,12 +2,25 @@
 #define __SR_GLOBAL_H__
 
 #include <stdint.h>
+#include <stm32f407xx.h>
+#include <stm32f4_isr.h>
+#include <sys/types.h>
 
 #define UNUSED(x) ((void) x)
 #define ARRAY_LENGTH(x) (sizeof(x) / sizeof(x[0]))
 
 #define unused_a __attribute__((unused))
 
+extern unsigned int sysclk_speed;
+extern unsigned int apb1_speed;
+extern unsigned int apb2_speed;
+extern unsigned int auxclk_speed;
+extern unsigned int apb1_timer_speed;
+extern unsigned int apb2_timer_speed;
+
+extern struct leds {
+    unsigned int comm_tx;
+} leds;
 static inline uint16_t htole(uint16_t val) { return val; }
 
 void __libc_init_array(void);
diff --git a/controller/fw/tinyprintf b/controller/fw/tinyprintf
new file mode 160000
+Subproject 2ee30120ec15e321566b43f83c731d060bb437f