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Added timer to insure I/O operations are fast enough for bit-bang

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This commit is contained in:
Bill Cox
2014-11-08 10:35:48 -05:00
parent 74a41705fb
commit 5951fd00dd
2 changed files with 30 additions and 7 deletions
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31
software/infnoise.c
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@@ -1,9 +1,13 @@
/* Driver for the Infinite Noise Multiplier USB stick */
// Required to include clock_gettime
#define _POSIX_C_SOURCE 200809L
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <ftdi.h>
#include "infnoise.h"
#include "KeccakF-1600-interface.h"
@@ -15,6 +19,10 @@
// This is how many previous bits are used to predict the next bit from the INM
#define PREDICTION_BITS 14
// This is the maximum time we allow to pass to perform the I/O operations, since long
// delays can reduce entropy from the INM.
#define MAX_MICROSEC_FOR_SAMPLES 5000
// This is the gain of each of the two op-amp stages in the INM
#define DESIGN_K 1.82
@@ -220,6 +228,13 @@ static bool initializeUSB(struct ftdi_context *ftdic, char **message) {
return true;
}
// Return the differnece in the times as a double in microseconds.
static double diffTime(struct timespec *start, struct timespec *end) {
uint32_t seconds = end->tv_sec - start->tv_sec;
int32_t nanoseconds = end->tv_nsec - start->tv_nsec;
return seconds*1e6 + nanoseconds/1000.0;
}
int main(int argc, char **argv)
{
struct ftdi_context ftdic;
@@ -290,6 +305,9 @@ int main(int argc, char **argv)
}
while(true) {
struct timespec start;
clock_gettime(CLOCK_REALTIME, &start);
if(ftdi_write_data(&ftdic, outBuf, BUFLEN) != BUFLEN) {
fputs("USB write failed\n", stderr);
return -1;
@@ -298,10 +316,15 @@ int main(int argc, char **argv)
fputs("USB read failed\n", stderr);
return -1;
}
uint8_t bytes[BUFLEN/8];
uint32_t entropy = extractBytes(bytes, inBuf, raw);
if(!noOutput && inmHealthCheckOkToUseData() && inmEntropyOnTarget(entropy, BUFLEN)) {
processBytes(keccakState, bytes, entropy, raw, writeDevRandom, outputMultiplier);
struct timespec end;
clock_gettime(CLOCK_REALTIME, &end);
uint32_t us = diffTime(&start, &end);
if(us <= MAX_MICROSEC_FOR_SAMPLES) {
uint8_t bytes[BUFLEN/8];
uint32_t entropy = extractBytes(bytes, inBuf, raw);
if(!noOutput && inmHealthCheckOkToUseData() && inmEntropyOnTarget(entropy, BUFLEN)) {
processBytes(keccakState, bytes, entropy, raw, writeDevRandom, outputMultiplier);
}
}
}
return 0;