Pito
Sun Jun 18, 2017 4:00 pm
While messing with the Zmodem example:
1. we miss the Serial.availableForWrite() method
2. when I look at the SerialUSB speed while printing out a bunch of strings (via Serial.print(F(..)) ) my impression is it runs like 9k6, I would guess it should be the fastest mode we’ve got.. Maybe I do something wrong?
1. we miss the Serial.availableForWrite() method
2. when I look at the SerialUSB speed while printing out a bunch of strings (via Serial.print(F(..)) ) my impression is it runs like 9k6, I would guess it should be the fastest mode we’ve got.. Maybe I do something wrong?
Pito
Sun Jun 18, 2017 4:59 pm
This is a bench for the Serial.print(F()) via SerialUSB (168MHz F407ZET):
UPDATE: println(F( vs. println(
UPDATE: println(F( vs. println(
// Serial.print(F()) via SerialUSB benchmark
// Pito 6/2017
void setup() {
Serial.begin(115200);
delay(3000);
uint32_t elapsed = micros();
for (uint32_t i = 0; i < 20; i++) {
Serial.println(F("THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST"));
}
elapsed = micros() - elapsed;
Serial.print("Elapsed with (F(: ");
Serial.print(elapsed);
Serial.println(" usecs");
Serial.println(" ");
elapsed = micros();
for (uint32_t i = 0; i < 20; i++) {
Serial.println("THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST");
}
elapsed = micros() - elapsed;
Serial.print("Elapsed: ");
Serial.print(elapsed);
Serial.println(" usecs");
}
void loop() {
}
danieleff
Sun Jun 18, 2017 5:07 pm
F407VE
…
THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST
Elapsed: 198278 usecs
…
THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST THIS IS A TEST
Elapsed: 198278 usecs
Pito
Sun Jun 18, 2017 5:09 pm
That is 8x faster.. 
My clocks config:
My clocks config:
RCC_OscInitStruct.PLL.PLLM = 8;
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;Pito
Sun Jun 18, 2017 5:42 pm
Can somebody try under Win7, plz?
stevestrong
Sun Jun 18, 2017 6:46 pm
not generic, but just as comparison to libmaple F407Vet6:
Elapsed: 484 usecsPito
Sun Jun 18, 2017 6:59 pm
That is 3100x faster that mine.. So it seems it is something wrong with my F407ZET’s SerialUSB then 
Pito
Mon Jun 19, 2017 10:39 am
I’ve updated the benchmark above and:
1. with Serial.println(“THIS.. it takes 39971 usecs
2. with Serial.println(F(“THIS.. it takes 1496123 usecs
So it seems the “F” is the issue here.. (Black F407ZET)
1. with Serial.println(“THIS.. it takes 39971 usecs
2. with Serial.println(F(“THIS.. it takes 1496123 usecs
So it seems the “F” is the issue here.. (Black F407ZET)
Pito
Tue Jun 20, 2017 11:57 pm
@Daniel and Steve: I do not understand how you can get such speeds with printing with “F”.
When stepping with debugger through it, the “F” prints each char individually via USB (after each write(c) below I see a new char appears in the TeraTerm terminal)
When stepping with debugger through it, the “F” prints each char individually via USB (after each write(c) below I see a new char appears in the TeraTerm terminal)
size_t Print::print(const __FlashStringHelper *ifsh)
{
PGM_P p = reinterpret_cast<PGM_P>(ifsh);
size_t n = 0;
while (1) {
unsigned char c = pgm_read_byte(p++);
if (c == 0) break;
if (write(c)) n++;
else break;
}
return n;
}danieleff
Wed Jun 21, 2017 4:31 am
Libmaple has optimizes version of it
size_t Print::print(const __FlashStringHelper *ifsh)
{
return print(reinterpret_cast<const char *>(ifsh));
}stevestrong
Wed Jun 21, 2017 4:40 am
For libmaple this is the time for copying the strings to the Tx buffer.
Only at the 27th TEST… string gets the buffer full…
Only at the 27th TEST… string gets the buffer full…
Pito
Wed Jun 21, 2017 6:26 am
[danieleff – Wed Jun 21, 2017 4:31 am] –
Libmaple has optimizes version of it
size_t Print::print(const __FlashStringHelper *ifsh)
{
return print(reinterpret_cast<const char *>(ifsh));
}