add rng

targets/stm32l442/src/flash.h

@@ -1,5 +1,5 @@
-#ifndef _FLASH_H_H
-#define _FLASH_H_H
+#ifndef _FLASH_H_
+#define _FLASH_H_
 
 void flash_erase_page(uint8_t page);
 void flash_write_dword(uint32_t addr, uint64_t data);

targets/stm32l442/src/init.c

@@ -11,6 +11,7 @@
 #include "stm32l4xx_ll_usart.h"
 #include "stm32l4xx_ll_bus.h"
 #include "stm32l4xx_ll_tim.h"
+#include "stm32l4xx_ll_rng.h"
 
 /* USER CODE BEGIN Includes */
 
@@ -30,6 +31,7 @@ static void MX_GPIO_Init(void);
 static void MX_USART1_UART_Init(void);
 static void MX_TIM2_Init(void);
 static void MX_TIM6_Init(void);
+static void MX_RNG_Init(void);
 
 #define Error_Handler() _Error_Handler(__FILE__,__LINE__)
 void _Error_Handler(char *file, int line);
@@ -63,6 +65,7 @@ void hw_init(void)
   MX_TIM2_Init();
 
   MX_TIM6_Init();
+  MX_RNG_Init();
 
   TIM6->SR = 0;
   __enable_irq();
@@ -299,3 +302,14 @@ static void MX_TIM6_Init(void)
   // Start immediately
   LL_TIM_EnableCounter(TIM6);
 }
+
+/* RNG init function */
+static void MX_RNG_Init(void)
+{
+
+  /* Peripheral clock enable */
+  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_RNG);
+
+  LL_RNG_Enable(RNG);
+
+}

targets/stm32l442/src/main.c

@@ -15,13 +15,14 @@
 
 #include "app.h"
 #include "flash.h"
+#include "rng.h"
 
 #define Error_Handler() _Error_Handler(__FILE__,__LINE__)
 
 #define LED_PIN_G     LL_GPIO_PIN_0
 #define LED_PIN_B     LL_GPIO_PIN_1
 #define LED_PIN_R     LL_GPIO_PIN_2
-#define LED_PORT    GPIOA
+#define LED_PORT      GPIOA
 
 void hw_init(void);
 
@@ -140,11 +141,22 @@ void TIM6_DAC_IRQHandler()
     __65_seconds += 1;
 }
 
+void dump_hex(uint8_t * b, int len)
+{
+    while(len--)
+    {
+        printf("%02x ", *b++);
+    }
+    printf("\r\n");
+}
+
 int main(void)
 {
     uint8_t str[] = "YouCompleteMe: a code-completion engine for Vim";
-    uint8_t buf[500];
+    uint8_t buf[5000];
     uint32_t i = 0;
+    float ent;
+    float test = 1235.889944f;
     hw_init();
     printf("hello solo\r\n");
 
@@ -169,6 +181,12 @@ int main(void)
     uint32_t t2 = millis();
     printf("100 ms delay (%lu)\r\n",t2-t1);
 
+
+    ent = rng_test(64 * 1024);
+
+    printf("entropy of 64KB from RNG: %.6f\r\n", ent);
+    printf("test float: %.2f\r\n", test);
+
     // Test PWM + weighting of RGB
     test_colors();
 

targets/stm32l442/src/rng.c

@@ -0,0 +1,85 @@
+#include <math.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "stm32l4xx_ll_rng.h"
+
+#include "rng.h"
+
+int __errno = 0;
+
+void rng_get_bytes(uint8_t * dst, size_t sz)
+{
+    uint8_t r[8];
+    unsigned int i,j;
+    for (i = 0; i < sz; i += 4)
+    {
+        while( !LL_RNG_IsActiveFlag_DRDY(RNG) )
+            ;
+        *(uint32_t*)&r = LL_RNG_ReadRandData32(RNG);
+
+        if (RNG->SR & 0x66)
+        {
+            printf("Error RNG: %02lx\r\n", RNG->SR);
+            exit(1);
+        }
+
+        for (j = 0; j < 4; j++)
+        {
+            if ((i + j) > sz)
+            {
+                return;
+            }
+            dst[i + j] = r[j];
+        }
+    }
+}
+
+float shannon_entropy(float * p, size_t sz)
+{
+
+    unsigned int i;
+    float entropy = 0.0f;
+
+    for(i=0; i < sz; i++)
+    {
+        if (p[i] > 0.0)
+        {
+            entropy -= p[i] * (float) log( (double) p[i]);
+        }
+    }
+
+    entropy = entropy / (float) log ((double) 2.0);
+
+    return entropy;
+}
+
+// Measure shannon entropy of RNG 
+float rng_test(size_t n)
+{
+    unsigned int i;
+    int sz = 0;
+    uint8_t buf[4];
+    int counts[256];
+    float p[256];
+
+    memset(counts, 0, sizeof(counts));
+
+    for(i=0; i < n; i+=4)
+    {
+        rng_get_bytes(buf, 4);
+        sz += 4;
+
+        counts[buf[0]]++;
+        counts[buf[1]]++;
+        counts[buf[2]]++;
+        counts[buf[3]]++;
+    }
+
+    for (i = 0; i < 256; i++)
+    {
+        p[i] = ((float)counts[i])/sz;
+    }
+
+    return shannon_entropy(p, 256);
+}

targets/stm32l442/src/rng.h

@@ -0,0 +1,9 @@
+#ifndef _RNG_H_
+#define _RNG_H_
+#include <stdint.h>
+
+void rng_get_bytes(uint8_t * dst, size_t sz);
+float shannon_entropy(float * p, size_t sz);
+float rng_test(size_t n);
+
+#endif