Hi Mike,
can you please explain how the trunc function works and how it is called by QSPICE, so I can understand the mechanism better?
I’m trying to build a pwm block that works pretty much like it would in an microcontroller, i.e. ramps and compare values. to get precise edges while not enforcing a continuous small timestep, I’m using the trunc function. this works quite well but in some cases an out port doesn’t reflect the internal value (checked with printf) and I don’t get why.
It let’s you give a temporal tolerance in addition to the normal volt, current, and charge tolerances. Study the example “PracticalSMPS.qsch” It’s there to illustrate its use.
–Mike
ah … yes … learning by reverse engineering. I love spending hours trying to understand something that could be explained with a view lines of text or a diagram. Also I’m not asking about how to use it, but how it is working, so I may have a better chance for debugging what is not working.
But ok, I try myself :
Schematic:
// Automatically generated C++ file on Thu Aug 17 23:16:22 2023
//
// To build with Digital Mars C++ Compiler:
//
// dmc -mn -WD ctest_x1.cpp kernel32.lib
#include <stdio.h>
#include <malloc.h>
#include <stdarg.h>
#include <time.h>
union uData
{
bool b;
char c;
unsigned char uc;
short s;
unsigned short us;
int i;
unsigned int ui;
float f;
double d;
long long int i64;
unsigned long long int ui64;
char *str;
unsigned char *bytes;
};
// int DllMain() must exist and return 1 for a process to load the .DLL
// See https://docs.microsoft.com/en-us/windows/win32/dlls/dllmain for more information.
int __stdcall DllMain(void *module, unsigned int reason, void *reserved) { return 1; }
void display(const char *fmt, ...)
{ // for diagnostic print statements
msleep(30);
fflush(stdout);
va_list args = { 0 };
va_start(args, fmt);
vprintf(fmt, args);
va_end(args);
fflush(stdout);
msleep(30);
}
void bzero(void *ptr, unsigned int count)
{
unsigned char *first = (unsigned char *) ptr;
unsigned char *last = first + count;
while(first < last)
*first++ = '\0';
display("bzero\n");
display("[sample time + count]\n");
}
// #undef pin names lest they collide with names in any header file(s) you might include.
#undef in
#undef out
struct sCTEST_X1
{
// declare the structure here
bool state;
bool trunc;
int n_pwm;
int n;
};
extern "C" __declspec(dllexport) void ctest_x1(struct sCTEST_X1 **opaque, double t, union uData *data)
{
double &out = data[0].d; // output
double &dbg = data[1].d; // output
if(!*opaque)
{
*opaque = (struct sCTEST_X1 *) malloc(sizeof(struct sCTEST_X1));
bzero(*opaque, sizeof(struct sCTEST_X1));
}
struct sCTEST_X1 *inst = *opaque;
// Implement module evaluation code here:
static int n = 0;
static int nt = 0;
bool toggle = false;
double T = 10e-6;
double tpwm = t - inst->n_pwm * T;
dbg = tpwm;
// sample point counter
if (t > 0) inst->n++; // don't count t=0 steps
if (inst->trunc) {
nt++; // call counter called from trunc
display("\t\t\t\t%4u\t\t\tmain called from Trunc (n=%u)\n", inst->n, nt);
}
else {
n++; // call counter called from ?
display("%8.3fns\t%4u\t\tmain called from Qspice? (n=%u)\n", t*1e9, inst->n, n);
display("\t\t\t\t\t\t\t\t=> outputs determined for t=%8.3fns\n", t*1e9);
}
// set high
if (!out && tpwm > 0.5*T) {
out = true;
toggle = true;
if (inst->trunc) display("\t\t\t\t\t\t\t\tout is LOW, but would be HIGH next step\n");
else display("\t\t\t\t\t\t\t\tout is HIGH\n");
}
// set low
if (tpwm >= T) {
inst->n_pwm++;
out = false;
toggle = true;
if (inst->trunc) display("\t\t\t\t\t\t\t\tout is HIGH, but would be LOW next step\n");
else display("\t\t\t\t\t\t\t\tout is LOW\n");
}
inst->state ^= toggle;
}
extern "C" __declspec(dllexport) double MaxExtStepSize(struct sCTEST_X1 *inst)
{
static int sn = 0;
sn++;
display("\n\t\t\t\t%4u\t\tMaxExtStepSize called from Qspice?\n", inst->n);
display("\t\t\t\t\t\t\t\t=> returns max_timestep=1e-6 (n=%u)\n", sn);
return 1e-6; // implement a good choice of max timestep size that depends on struct sCTEST_X1
}
extern "C" __declspec(dllexport) void Trunc(struct sCTEST_X1 *inst, double t, union uData *data, double *timestep)
{ // limit the timestep to a tolerance if the circuit causes a change in struct sCTEST_X1
const double ttol = 10e-9;
static int n = 0; // call counter
n++;
display("%8.3fns\t%4u\t\tTrunc called from Qspice? (n=%u)\n", t*1e9, inst->n, n);
if(*timestep > ttol) // *timestep seems to be always inf.
{
double &out = data[0].d; // output
double &dbg = data[1].d; // output
// Save output vector
const double _out = out;
const double _dbg = dbg;
struct sCTEST_X1 tmp = *inst;
tmp.trunc = true; // to signal it was called from trunc
ctest_x1(&(&tmp), t, data);
if(tmp.state != inst->state) {
*timestep = ttol;
display("\t\t\t\t\t\t\t\ttrunc: STATE CHANGE DETECTED, next timestep=%.1fns. Outputs restored.\n", (*timestep)*1e9);
}
else {
display("\t\t\t\t\t\t\t\ttrunc: no state change detected, next timestep=%.1fns. Outputs restored.\n", (*timestep)*1e9);
}
// Restore output vector
out = _out;
dbg = _dbg;
}
else {
display("*timestep <= ttol");
}
}
extern "C" __declspec(dllexport) void Destroy(struct sCTEST_X1 *inst)
{
display("Destroy.");
free(inst);
}
Waveform looks like this:
bzero
[sample time + count]
0.000ns 0 main called from Qspice? (n=1)
=> outputs determined for t= 0.000ns
0.000ns 0 main called from Qspice? (n=2)
=> outputs determined for t= 0.000ns
0.000ns 0 main called from Qspice? (n=3)
=> outputs determined for t= 0.000ns
0.000ns 0 main called from Qspice? (n=4)
=> outputs determined for t= 0.000ns
0.000ns 0 main called from Qspice? (n=5)
=> outputs determined for t= 0.000ns
0.000ns 0 main called from Qspice? (n=6)
=> outputs determined for t= 0.000ns
0 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=1)
1000.000ns 1 main called from Qspice? (n=7)
=> outputs determined for t=1000.000ns
1 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=2)
2000.000ns 1 Trunc called from Qspice? (n=1)
2 main called from Trunc (n=1)
trunc: no state change detected, next timestep=infns. Outputs restored.
2000.000ns 1 Trunc called from Qspice? (n=2)
2 main called from Trunc (n=2)
trunc: no state change detected, next timestep=infns. Outputs restored.
2000.000ns 2 main called from Qspice? (n=8)
=> outputs determined for t=2000.000ns
2 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=3)
3000.000ns 2 Trunc called from Qspice? (n=3)
3 main called from Trunc (n=3)
trunc: no state change detected, next timestep=infns. Outputs restored.
3000.000ns 2 Trunc called from Qspice? (n=4)
3 main called from Trunc (n=4)
trunc: no state change detected, next timestep=infns. Outputs restored.
3000.000ns 3 main called from Qspice? (n=9)
=> outputs determined for t=3000.000ns
3 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=4)
4000.000ns 3 Trunc called from Qspice? (n=5)
4 main called from Trunc (n=5)
trunc: no state change detected, next timestep=infns. Outputs restored.
4000.000ns 3 Trunc called from Qspice? (n=6)
4 main called from Trunc (n=6)
trunc: no state change detected, next timestep=infns. Outputs restored.
4000.000ns 4 main called from Qspice? (n=10)
=> outputs determined for t=4000.000ns
4 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=5)
5000.000ns 4 Trunc called from Qspice? (n=7)
5 main called from Trunc (n=7)
trunc: no state change detected, next timestep=infns. Outputs restored.
5000.000ns 5 main called from Qspice? (n=11)
=> outputs determined for t=5000.000ns
5 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=6)
6000.000ns 5 Trunc called from Qspice? (n=8)
6 main called from Trunc (n=8)
out is LOW, but would be HIGH next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
5010.000ns 5 Trunc called from Qspice? (n=9)
6 main called from Trunc (n=9)
out is LOW, but would be HIGH next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
5010.000ns 6 main called from Qspice? (n=12)
=> outputs determined for t=5010.000ns
out is HIGH
6 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=7)
5020.000ns 6 Trunc called from Qspice? (n=10)
7 main called from Trunc (n=10)
trunc: no state change detected, next timestep=infns. Outputs restored.
5020.000ns 7 main called from Qspice? (n=13)
=> outputs determined for t=5020.000ns
7 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=8)
5040.000ns 7 Trunc called from Qspice? (n=11)
8 main called from Trunc (n=11)
trunc: no state change detected, next timestep=infns. Outputs restored.
5040.000ns 8 main called from Qspice? (n=14)
=> outputs determined for t=5040.000ns
8 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=9)
5080.000ns 8 Trunc called from Qspice? (n=12)
9 main called from Trunc (n=12)
trunc: no state change detected, next timestep=infns. Outputs restored.
5080.000ns 9 main called from Qspice? (n=15)
=> outputs determined for t=5080.000ns
9 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=10)
5160.000ns 9 Trunc called from Qspice? (n=13)
10 main called from Trunc (n=13)
trunc: no state change detected, next timestep=infns. Outputs restored.
5160.000ns 10 main called from Qspice? (n=16)
=> outputs determined for t=5160.000ns
10 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=11)
5320.000ns 10 Trunc called from Qspice? (n=14)
11 main called from Trunc (n=14)
trunc: no state change detected, next timestep=infns. Outputs restored.
5320.000ns 11 main called from Qspice? (n=17)
=> outputs determined for t=5320.000ns
11 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=12)
5640.000ns 11 Trunc called from Qspice? (n=15)
12 main called from Trunc (n=15)
trunc: no state change detected, next timestep=infns. Outputs restored.
5640.000ns 12 main called from Qspice? (n=18)
=> outputs determined for t=5640.000ns
12 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=13)
6280.000ns 12 Trunc called from Qspice? (n=16)
13 main called from Trunc (n=16)
trunc: no state change detected, next timestep=infns. Outputs restored.
6280.000ns 13 main called from Qspice? (n=19)
=> outputs determined for t=6280.000ns
13 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=14)
7280.000ns 13 Trunc called from Qspice? (n=17)
14 main called from Trunc (n=17)
trunc: no state change detected, next timestep=infns. Outputs restored.
7280.000ns 14 main called from Qspice? (n=20)
=> outputs determined for t=7280.000ns
14 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=15)
8280.000ns 14 Trunc called from Qspice? (n=18)
15 main called from Trunc (n=18)
trunc: no state change detected, next timestep=infns. Outputs restored.
8280.000ns 15 main called from Qspice? (n=21)
=> outputs determined for t=8280.000ns
15 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=16)
9280.000ns 15 Trunc called from Qspice? (n=19)
16 main called from Trunc (n=19)
trunc: no state change detected, next timestep=infns. Outputs restored.
9280.000ns 16 main called from Qspice? (n=22)
=> outputs determined for t=9280.000ns
16 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=17)
10280.000ns 16 Trunc called from Qspice? (n=20)
17 main called from Trunc (n=20)
out is HIGH, but would be LOW next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
9290.000ns 16 Trunc called from Qspice? (n=21)
17 main called from Trunc (n=21)
trunc: no state change detected, next timestep=infns. Outputs restored.
9290.000ns 17 main called from Qspice? (n=23)
=> outputs determined for t=9290.000ns
17 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=18)
9310.000ns 17 Trunc called from Qspice? (n=22)
18 main called from Trunc (n=22)
trunc: no state change detected, next timestep=infns. Outputs restored.
9310.000ns 18 main called from Qspice? (n=24)
=> outputs determined for t=9310.000ns
18 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=19)
9350.000ns 18 Trunc called from Qspice? (n=23)
19 main called from Trunc (n=23)
trunc: no state change detected, next timestep=infns. Outputs restored.
9350.000ns 19 main called from Qspice? (n=25)
=> outputs determined for t=9350.000ns
19 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=20)
9430.000ns 19 Trunc called from Qspice? (n=24)
20 main called from Trunc (n=24)
trunc: no state change detected, next timestep=infns. Outputs restored.
9430.000ns 20 main called from Qspice? (n=26)
=> outputs determined for t=9430.000ns
20 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=21)
9590.000ns 20 Trunc called from Qspice? (n=25)
21 main called from Trunc (n=25)
trunc: no state change detected, next timestep=infns. Outputs restored.
9590.000ns 21 main called from Qspice? (n=27)
=> outputs determined for t=9590.000ns
21 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=22)
9910.000ns 21 Trunc called from Qspice? (n=26)
22 main called from Trunc (n=26)
trunc: no state change detected, next timestep=infns. Outputs restored.
9910.000ns 22 main called from Qspice? (n=28)
=> outputs determined for t=9910.000ns
22 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=23)
10550.000ns 22 Trunc called from Qspice? (n=27)
23 main called from Trunc (n=27)
out is HIGH, but would be LOW next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
9920.000ns 22 Trunc called from Qspice? (n=28)
23 main called from Trunc (n=28)
trunc: no state change detected, next timestep=infns. Outputs restored.
9920.000ns 23 main called from Qspice? (n=29)
=> outputs determined for t=9920.000ns
23 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=24)
9940.000ns 23 Trunc called from Qspice? (n=29)
24 main called from Trunc (n=29)
trunc: no state change detected, next timestep=infns. Outputs restored.
9940.000ns 24 main called from Qspice? (n=30)
=> outputs determined for t=9940.000ns
24 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=25)
9980.000ns 24 Trunc called from Qspice? (n=30)
25 main called from Trunc (n=30)
trunc: no state change detected, next timestep=infns. Outputs restored.
9980.000ns 25 main called from Qspice? (n=31)
=> outputs determined for t=9980.000ns
25 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=26)
10060.000ns 25 Trunc called from Qspice? (n=31)
26 main called from Trunc (n=31)
out is HIGH, but would be LOW next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
9990.000ns 25 Trunc called from Qspice? (n=32)
26 main called from Trunc (n=32)
trunc: no state change detected, next timestep=infns. Outputs restored.
9990.000ns 26 main called from Qspice? (n=32)
=> outputs determined for t=9990.000ns
26 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=27)
10010.000ns 26 Trunc called from Qspice? (n=33)
27 main called from Trunc (n=33)
out is HIGH, but would be LOW next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
10000.000ns 26 Trunc called from Qspice? (n=34)
27 main called from Trunc (n=34)
trunc: no state change detected, next timestep=infns. Outputs restored.
10000.000ns 27 main called from Qspice? (n=33)
=> outputs determined for t=10000.000ns
27 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=28)
10020.000ns 27 Trunc called from Qspice? (n=35)
28 main called from Trunc (n=35)
out is HIGH, but would be LOW next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
10010.000ns 27 Trunc called from Qspice? (n=36)
28 main called from Trunc (n=36)
out is HIGH, but would be LOW next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
10010.000ns 28 main called from Qspice? (n=34)
=> outputs determined for t=10010.000ns
out is LOW
28 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=29)
10020.000ns 28 Trunc called from Qspice? (n=37)
29 main called from Trunc (n=37)
trunc: no state change detected, next timestep=infns. Outputs restored.
10020.000ns 29 main called from Qspice? (n=35)
=> outputs determined for t=10020.000ns
29 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=30)
10040.000ns 29 Trunc called from Qspice? (n=38)
30 main called from Trunc (n=38)
trunc: no state change detected, next timestep=infns. Outputs restored.
10040.000ns 30 main called from Qspice? (n=36)
=> outputs determined for t=10040.000ns
30 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=31)
10080.000ns 30 Trunc called from Qspice? (n=39)
31 main called from Trunc (n=39)
trunc: no state change detected, next timestep=infns. Outputs restored.
10080.000ns 31 main called from Qspice? (n=37)
=> outputs determined for t=10080.000ns
31 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=32)
10160.000ns 31 Trunc called from Qspice? (n=40)
32 main called from Trunc (n=40)
trunc: no state change detected, next timestep=infns. Outputs restored.
10160.000ns 32 main called from Qspice? (n=38)
=> outputs determined for t=10160.000ns
32 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=33)
10320.000ns 32 Trunc called from Qspice? (n=41)
33 main called from Trunc (n=41)
trunc: no state change detected, next timestep=infns. Outputs restored.
10320.000ns 33 main called from Qspice? (n=39)
=> outputs determined for t=10320.000ns
33 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=34)
10640.000ns 33 Trunc called from Qspice? (n=42)
34 main called from Trunc (n=42)
trunc: no state change detected, next timestep=infns. Outputs restored.
10640.000ns 34 main called from Qspice? (n=40)
=> outputs determined for t=10640.000ns
34 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=35)
11280.000ns 34 Trunc called from Qspice? (n=43)
35 main called from Trunc (n=43)
trunc: no state change detected, next timestep=infns. Outputs restored.
11280.000ns 35 main called from Qspice? (n=41)
=> outputs determined for t=11280.000ns
35 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=36)
12280.000ns 35 Trunc called from Qspice? (n=44)
36 main called from Trunc (n=44)
trunc: no state change detected, next timestep=infns. Outputs restored.
12280.000ns 36 main called from Qspice? (n=42)
=> outputs determined for t=12280.000ns
36 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=37)
13280.000ns 36 Trunc called from Qspice? (n=45)
37 main called from Trunc (n=45)
trunc: no state change detected, next timestep=infns. Outputs restored.
13280.000ns 37 main called from Qspice? (n=43)
=> outputs determined for t=13280.000ns
37 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=38)
14280.000ns 37 Trunc called from Qspice? (n=46)
38 main called from Trunc (n=46)
trunc: no state change detected, next timestep=infns. Outputs restored.
14280.000ns 38 main called from Qspice? (n=44)
=> outputs determined for t=14280.000ns
38 MaxExtStepSize called from Qspice?
=> returns max_timestep=1e-6 (n=39)
15280.000ns 38 Trunc called from Qspice? (n=47)
39 main called from Trunc (n=47)
out is LOW, but would be HIGH next step
trunc: STATE CHANGE DETECTED, next timestep=10.0ns. Outputs restored.
...
So what I get is something like the following, starting at:
time4 = 4000ns, outpus are already calculated
void Trunc(...))void ctest_x1(...)) with a temporary struct with time5= time4 + 1000ns = 5000nsso for one sample point the main funcition gets called 2 times.
time5 = 5000ns
inst->state is detected, temporary data is discarded, next timestep will be only 10nstime6=5010ns
for the next steps the timestep will get doubled until it gets limited to 1000ns again (if not reduced again in the meantime)
edit: updated code, output and text to make it clearer