From 09d1d12656f128ba534f5860f44f8716c5bd3957 Mon Sep 17 00:00:00 2001
From: Charlie Birks <charlie@daft.games>
Date: Sun, 5 Mar 2023 20:32:49 +0000
Subject: [PATCH] pico: use pico_rand for random API

It's the closest we're getting to a hardware RNG. Saves ~2.5k RAM.

(Requires pico-sdk 1.5.0)
---
 32blit-pico/CMakeLists.txt |  2 +-
 32blit-pico/main.cpp       | 22 +++-------------------
 2 files changed, 4 insertions(+), 20 deletions(-)

diff --git a/32blit-pico/CMakeLists.txt b/32blit-pico/CMakeLists.txt
index c52ce785d..b8e1d7fea 100644
--- a/32blit-pico/CMakeLists.txt
+++ b/32blit-pico/CMakeLists.txt
@@ -36,7 +36,7 @@ target_sources(BlitHalPico INTERFACE
     ${CMAKE_CURRENT_LIST_DIR}/usb_descriptors.c
 )
 
-target_link_libraries(BlitHalPico INTERFACE hardware_dma hardware_pio hardware_pwm hardware_spi pico_multicore pico_stdlib pico_unique_id tinyusb_device)
+target_link_libraries(BlitHalPico INTERFACE hardware_dma hardware_pio hardware_pwm hardware_spi pico_multicore pico_stdlib pico_unique_id pico_rand tinyusb_device)
 target_include_directories(BlitHalPico INTERFACE
     ${CMAKE_CURRENT_LIST_DIR} # for tusb_config
     ${CMAKE_CURRENT_LIST_DIR}/../3rd-party/fatfs
diff --git a/32blit-pico/main.cpp b/32blit-pico/main.cpp
index ccd3e0711..867302419 100644
--- a/32blit-pico/main.cpp
+++ b/32blit-pico/main.cpp
@@ -1,10 +1,10 @@
-#include <stdio.h>
-#include <random>
+#include <cstdio>
 
 #include "hardware/structs/rosc.h"
 #include "hardware/vreg.h"
 #include "pico/binary_info.h"
 #include "pico/multicore.h"
+#include "pico/rand.h"
 #include "pico/stdlib.h"
 
 #include "audio.hpp"
@@ -26,24 +26,8 @@ static uint32_t now() {
   return to_ms_since_boot(get_absolute_time());
 }
 
-static uint32_t get_random_seed() {
-  uint32_t seed = 0;
-
-  // use the hardware random bit to seed
-  for(int i = 0; i < 32; i++) {
-    seed <<= 1;
-    seed |= rosc_hw->randombit & 1;
-    sleep_us(1); // don't read too fast
-  }
-
-  return seed;
-}
-
 static uint32_t random() {
-  static std::mt19937 random_generator(get_random_seed());
-  static std::uniform_int_distribution<uint32_t> random_distribution;
-
-	return random_distribution(random_generator);
+	return get_rand_32();
 }
 
 static void debug(const char *message) {