crc.c is ready now and works as required

software/signal_processing/crc.c

@@ -3,49 +3,74 @@
 #include "system/float_word.h"
 //#include <zlib.h> 				/* c-library for crc32() */
 #include <stddef.h>					/* for "size_t" */
+#include <stdio.h>
 
+#if 0
+#define PRINT_DEBUG_VALUES
+#endif
 
-uint32_t crc32(const char *s,size_t n) {
-	uint32_t crc=0xFFFFFFFF;
-	for(size_t i=0;i<n;i++) 
+
+/* used basic algo from and modified it: https://lxp32.github.io/docs/a-simple-example-crc32-calculation/*/
+uint32_t crc32(uint32_t *crc_res, const char *s,size_t n) 
+{
+	uint32_t crc = ~(*crc_res);		// always invert the input!
+
+	#ifdef PRINT_DEBUG_VALUES
+	printf("SIZE OF SEED, INPUT & OUTPUT: %i\n", n);	
+	printf("SEED:    %08x\n", *crc_res);	
+	printf("INPUT:   %08x\n", *(uint32_t*)s);
+	#endif /*PRINT_DEBUG_VALUES*/
+	
+	for(size_t i=0;i<n;++i) 
 	{
-		char ch=s[i];
-			for(size_t j=0;j<8;j++) {
+		unsigned char ch=s[i];
+
+		#ifdef PRINT_DEBUG_VALUES
+		printf("ch: %02x\n", ch);
+		#endif /*PRINT_DEBUG_VALUES*/
+
+		for(size_t j=0;j<8;++j) {
 				uint32_t b=(ch^crc)&1;
 				crc>>=1;
-				if(b) crc=crc^0xEDB88320;
+				//if(b) crc=crc^0x04C11DB7; // Polynomial representations: NORMAL
+				if(b) crc=crc^0xEDB88320; // Polynomial representations: REVERSED
 				ch>>=1;
 		}
 	}
+
+	#ifdef PRINT_DEBUG_VALUES
+	printf("OUTPUT:  %08x\n", crc);
+	printf("~OUTPUT: %08x\n", ~crc);
+	getchar();		// just here for debugging step by step
+	#endif /*PRINT_DEBUG_VALUES*/
+
 	return ~crc;
 }
 
 
 
 
-int task_crc_run( void * task ) {
-
+int task_crc_run( void * task )
+{
     // TODO
 
 	crc_config * crc = ( crc_config * ) task;
 	uint32_t data_channel_base = crc->base.sink;
 	data_channel_clear( data_channel_base);
-
+		
 	float_word crc_res;
 	float_word crc_input;
 
+	crc_res.word = crc->start;
+
 	for ( uint32_t i = 0; i < DATA_CHANNEL_DEPTH; ++i )
 	{
 		data_channel_read(crc->base.sources[0], (uint32_t*)&crc_input.value);
-		
-		crc_res.word = crc32((const void *)&crc_input, sizeof(crc_input));
-	
+		crc_res.word = crc32(&crc_res.word,(const void *)&crc_input, sizeof(crc_input));
 	}
 
-
 	data_channel_write( data_channel_base, crc_res.word );
 
-
     return 0;
 }