Added basic support for CH32V003.

impl/random.h

@@ -33,6 +33,8 @@ static TLS struct {
 #    include "random/rtthread.h"
 #elif defined(CH32V30x_D8) || defined(CH32V30x_D8C)
 #    include "random/ch32.h"
+#elif defined(CH32V0XX)
+#    include "random/ch32v0xx.h"
 #elif defined(CHIBIOS)
 #    include "random/chibios.h"
 #else

impl/random/ch32v0xx.h

@@ -0,0 +1,100 @@
+/**********************************************************************************
+ * File Name          : ch32v0xx.h (Tentative)
+ * Author             : Charles Lee Scoville
+ * Version            : V0.0.2 (Pull request #153 modifications)
+ * Start Date         : 2024/01/02
+ * Description        : TRNG initialization shim
+ *
+ * The CH32V0XX does not have a hardware random number generator. This leaves us with
+ * only a few options for collecting entropy.
+ *
+ *  - Attach an entropy source circuit to the chip. (biased Zener, transistor, etc.)
+ *  - Use uninitialized data from SRAM proceeding chip power on.
+ *  - Timing difference (jitter) between two *independent* clock sources.
+ *  - Read some voltage with the ADC and look only at low bit(s).
+ *
+ *  *TODO* I intend to survey all options and make code for each, and a complete
+ *  write up. Until then, at least I have something working today. Tangible PoC
+ *  beats "good ideas" that haven't been written yet any day.
+ *
+ *  *TODO* Compilation flags to switch between the different entropy options
+ *  in a way that is transparent to this shim would be really neato.
+ *********************************************************************************/
+
+#include <ch32v00x.h>
+
+/* This must be defined in your CH32V003 project, and must be filled with raw /
+ * unfiltered samples from the internal reference voltage, as the name implies*/
+extern uint16_t ADC_Channel_Vrefint_value;
+
+
+uint32_t entropy_condenser_extractor(void) {
+
+	volatile uint64_t entropy_buffer = 0;
+	volatile uint8_t entropy_buffer_count = 0;
+
+	volatile uint32_t extract = 0;
+	volatile uint8_t extract_count = 0;
+	volatile FlagStatus extract_RDY = RESET;
+
+	if ( !((ADC1->CTLR2 & 1) != 0) )
+		while(1); /* ADC1 OFF!!! PANIK! */
+
+    while (extract_RDY == RESET) {
+
+    	volatile uint32_t compare = ADC_Channel_Vrefint_value;
+
+		/* Wait for new ADC data */
+		while (compare == ADC_Channel_Vrefint_value)
+			__NOP();
+
+
+		entropy_buffer = entropy_buffer << 1;
+
+		entropy_buffer = entropy_buffer + ((ADC_Channel_Vrefint_value & 0x40) == 0x40);
+
+		entropy_buffer_count++;
+		if (entropy_buffer_count > 63) {
+			entropy_buffer_count = 0;
+
+			for (uint8_t j = 0; (j < 31); j++) {
+
+				/* 64->32 bit Von Neuman extractor */
+				if ((entropy_buffer & 1) ^ ((entropy_buffer >> 1) & 1)) {
+					extract = (extract << 1)+((entropy_buffer >> 1) & 1);
+					extract_count++;
+				}
+
+				entropy_buffer = entropy_buffer >> 2;
+
+				if (extract_count > 31) {
+					extract_count = 0;
+					extract_RDY = SET;
+				}
+			}
+		}
+    }
+	return extract;
+}
+
+
+extern int hydro_random_init(void) {
+    const char       ctx[hydro_hash_CONTEXTBYTES] = {'h','y','d','r','o','P','R','G'};
+    hydro_hash_state st;
+    uint16_t         ebits = 0;
+
+    hydro_hash_init(&st, ctx, NULL);
+
+    while (ebits < 512) {
+
+        uint32_t r = entropy_condenser_extractor();
+
+        hydro_hash_update(&st, (const uint32_t *) &r, sizeof r);
+        ebits += 32;
+    }
+
+    hydro_hash_final(&st, hydro_random_context.state, sizeof hydro_random_context.state);
+    hydro_random_context.counter = ~LOAD64_LE(hydro_random_context.state);
+
+    return 0;
+}