usbcnc / grbl Goto Github PK

Props on the good work for this Project!

I followed your instructions on the how to build and run GRBL video. I built the project in coocox. Set the Bootpin 0 to High and flashed the created .hex file with ST Flash Loader Demonstrator via serial connection.

I connected pc to board usb (shows up as STM Serial Com12) and used Universal Gcode Sender to connect to GRBL ( Com12, Baud11520, Firmware GRBL). This is the output i get from consol:

**** Connected to COM12 @ 115200 baud ****

Grbl 1.1f ['$' for help]

$$
$G
$0=10
$1=0
$2=7
$3=7
$4=0
$5=0
$6=0
$10=1
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=1
$23=3
$24=25.000
$25=500.000
$26=250
$27=1.500
$30=100
$31=0
$32=0
$100=400.000
$101=400.000
$102=400.000
$110=600.000
$111=600.000
$112=600.000
$120=45.000
$121=45.000
$122=45.000
$130=200.000
$131=300.000
$132=50.000
ok
[verbose]GrblFeedbackMessage{message='[GC:G0 G54 G17 G21 G90 G94 M5 M M9 T0 F0 S0]', distanceMode='G90', units='G21'}
[GC:G0 G54 G17 G21 G90 G94 M5 M M9 T0 F0 S0]
ok
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P|WCO:0.000,0.000,0.000>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P|Ov:100,100,100|A:S>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P|WCO:0.000,0.000,0.000>
[verbose]<Alarm|MPos:0.000,0.000,0.000|FS:0,0|Pn:P|Ov:100,100,100|A:S>

From there on the output just loops and the Machine status from UGCS is Active State: Alarm.

My question is, did i do something wrong and how can i resolve it?Or is this a code/port based problem?

Thanks for your work on the project :) cheers

To control my STM32F103 I use bCNC.
The STM32 is programmed with the latest firmware as is.

Now I tried some gray scale images but it seems the laser is on of off, nothing in between.
Did I miss something in the code as VARIABLE_SPINDLE is defined in the config.h file.
A have it connected to pin A8 is mentioned in the file cpu_map.h

Is variable spindle speed implemented?

is there any chances to port it to GRBL v1.1f ?

Hi there

first thanks for your work to port GRBL to the STM32!

i've managed to Flash mine and run it.

the only Thing i've not found out yet is the pinout:

from this Picture:

http://wiki.stm32duino.com/images/a/ae/Bluepillpinout.gif

i've seen the labled Pins in relationship to arduino

but if i connect for instance A2 as X-step and A5 as X-dir the stepper doesnt move... Any idea?

Hi,

with my setup (STM32 Blue Pill) some chars sent over USB get corrupted in transmission. eg. I get the occasional [BRB:] instead of PRB, sometimes status messages have some wrong characters (both in text and numbers). I have yet to find an error in the transmission from the PC to grbl.

I'm using a single USB cable which is relatively short, though this shouldn't affect the data anyways as USB normally uses CRC. Is CRC disabled for incoming messages like in vUSB? This would explain why (so far) only messages from the PC have been corrupted.

Martin

Hi @usbcnc
I want to port to STM32F469-DIS
Is there a good way to get started?
It seems that to modify PIN Map, Right?
Thanks to your help.

many .bak files were committed in the last committ. Should be removed.

thanks @usbcnc for porting to such platform , however I've tried to change it and uploaded to my board regards to instructions , I think it little be handy , do you have plan to port it base on Roger Clarck repo, its very stable now ?

Hello USBCNC,

I flashed an older hex file you provided here on a blue pill STM32F103C8T6 board, installed ST's VCP driver and did a first test.
I streamed a pretty big g-code file (860.000 lines, running time ~2hours) using bCNC -> this works without a problem.

However, the same test using a self-compiled file only works for a few minutes but after some random time (between 5 and 15 minutes) it hangs.

I already tried different compiler options and optimization levels but can't get it to work reliable.
A next test is to use an older compiler. I currently use 6.3.1-2017q2 and I think you used 4.9-2015q3 as I saw here.

Do you have any further ideas ?

I'm interested in a stable and reliable GRBL STM32 port, so any help is highly appreciated.

Thanks and best regards,
lakeroe

i try to connect a relay to PB3 fora coolant fan ,but thisnot work.if i change thr pin for coolant from PB3 to PA9 this work perfectly.
why happen that?
thank you for your work!!
and if you can help me with this!!!

Why is the pulse rate still limited to 30khz on a much faster board??

In file stepper.c, there is:
#ifndef WIN32
uint8_t step_pulse_time; // Step pulse reset time after step rise

For STM32, step_pulse_time is then filled with
#elif defined(STM32F103C8)
st.step_pulse_time = (settings.pulse_microseconds)*TICKS_PER_MICROSECOND;

As TICKS_PER_MICROSECOND = 72, it is not possible to assign more than 3 usec to the parameter pulse_microseconds because (settings.pulse_microseconds)*TICKS_PER_MICROSECOND would exceed 255.
To solve this, we should define step_pulse_time as uint16_t or we should apply a prescaler for the timer (for stm32F103).

Has anyone tried homing and knows if it works?

I have limit triggers that I know works with the atmega-version. So the hardware should not be a problem.

When I view "?" output it reports the triggers correctly in all axis.
I have the triggers at a high level and goes to a low when triggered.
As soon as I try the $H it homes the axis and pulls off, but then locks up and reports Alarm 7.

I've tried to enable the safety door, but it does not make a difference.

Every thing works fine and very nice. there are only error:2 and error:11 are annoyed.
By Universal gcode sender shows error:2. So try writing small program in C for only reading serial data to see what, find error:2 and error:11 in my reading loop. these quite weird for me. I try to find what the cause of these problems, but cannot position them.
Can any one help?

i try to enable PB3 for a coolant ,and nothingh works,so i assign PA 9 for this function(turn on-off a fan whit M8-M9 commands)i tested ,and allseems work fine,i not have many knowledge about this board,so this is not the way to activate a fan coolant please excuse and let me know the righ way to do that.thank you so much!!!

sorry to open ticket for my question but actually I've tired to build cnc laser controller with Arduino compatible STF103CT6 board , however I've bit lost to assign the pins to the boards ,little hint really appreciated

In TIM2_IRQHandler from stepper.c, after DIRECTION pins are written, interrupts on TIM3 are enabled with code
NVIC_EnableIRQ(TIM3_IRQn);
Still, TIM3->CNT is not reset to 0. As TIM3 was not disabled (only reset to 0 by his IRQ handler), CNT can have any value.
So we can't be sure that the step pulse will have the expected delay.
To solve this, I think you have to force a reload of TIM3 registers and clear interrupts just before enabling interrupt again.
So add
TIM3->EGR = TIM_PSCReloadMode_Immediate;
TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
just before
NVIC_EnableIRQ(TIM3_IRQn);

Then, I think also that lines
TIM3->SR &= ~(1<<0); // clear UIF flag
TIM3->CNT = 0;
can be removed from TIM3_IRQHandler

We know grbl@arduino, pulse feq is about 30khz, what now upgrade to 32bit@72MHz?

For instance:

• by default all input pins with pull-up,
• you can remap CTRL_ pins only within pb5-pb9 (or pa5-pa9),
• you can remap limit pins only within pb10-pb15 (or pa10-pa15),
• e.t.c

USEUSB was defined symbols in configuration, there is still free IO pins left.
It's because I want try ESP8266 websocket connection and keep USB VCP support, toggle it by a jumpper or a switch on the panel. @usbcnc could you support it as enhancement? or the both port working together maybe a good idea?

I managed to compile the project on Linux with gcc and Make but after flashing stm32f103c8t6 with hex file USB fails to enumerate. I tried to use 1.8k resistor from 3.3v to pa12 but that didnt do anything. On other hand generic maple hex uploads and shows fine as USB device even without resistor.

I tried several forks of this project but same thing happens. Am I missing something? Do I need to do something else as well?

CoIDE dont exist but project compiles fine on Linux with eabi toolchain.

My Stm32f103 for Jog is OK, but if look at the code at line 857 in gcode.c. I find it quite not correct for condition check. This finds when I use this parser to make gcode analysis in my project on Linux. I get " invalid jog command error". Please see for the "bit instruction" as below.

if (command_words & ~(bit(MODAL_GROUP_G3) |
bit(MODAL_GROUP_G6 | bit(MODAL_GROUP_G0)) )) ->#note: this is quite not correct
{ FAIL(STATUS_INVALID_JOG_COMMAND) };

Hi, files are missing for making makefile works.
/STM32F103C8T6.ld (linker file)
/build/grbl-stm32.map
Please find included Archive.zip

Additionnally, makefile should refer to the correct buildddir and not debug dir:
BUILDDIR = build

In order to use those pins, the code has to ask a remap of pin and to activate a clock (RCC_APB2Periph_AFIO).

Therefore in main.c you currently have
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);

Still this line is active only if you are using UART1 instead of USB.
Quite similar line of code exist for "limits" and "controls" files but not in stepper.c
So I expect (but not tested it), that it will not be possible to use those pins for step, dir or enable stepper when USB is used instead of uart1.
It would be better to add a line in main.c in order to ALWAYS activate RCC_APB2Periph_AFIO

Hello,

for my application I need a separate spindle enable pin. With default settings PB13 is not working as expected. For this reason I uncommented following line in config.h
#define USE_SPINDLE_DIR_AS_ENABLE_PIN
This leads to an compilation error and I had to add "&& !defined(CPU_MAP_STM32F103)" in line 123 in grbl.h
Now it compiles fine and PB13 works as expected.
I just don't know if this is the intended way to do ...

Best regards,
lakeroe

Maybe not such a big deal, but using pin 2 for the coolant bit might not be so good since it's also the boot pin. Perhaps move it?

I'm very new to this architecture so i'm sorry if I'm mistaken.

On Maple mini board, PB9 is used to reset usb port throught a stage with 2 transistors. Unitialised state acts as an output to '1' and drive those transistors, resetting USB port.

Since PB9 is unused on current pin mapping, it coulb be initialsed ans output to 0, and leaved as is...
I've tested in main loop. Maple mini is properly enumarated on USB now.

....
#else
int main(void)
#endif
{#if defined (STM32F103C8)
	GPIO_InitTypeDef GPIO_InitStructure;
#ifdef LEDBLINK
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
	GPIO_Init(GPIOC, &GPIO_InitStructure);     
#endif

	// init PB9 as out port for maple mini
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
	GPIO_Init(COOLANT_FLOOD_PORT, &GPIO_InitStructure);
	GPIO_WriteBit(GPIOB, GPIO_Pin_9, Bit_RESET);
....

Normal (AVR) GRBL code supports #define STEP_PULSE_DELAY (in stepper.c)
This parameter allows to add a delay between setting the DIRECTION pins and the start of the STEP pulse in the stepper.c file.
This can be important because many stepper drivers ask for such a delay.
I would like to use some cheap clone of TB6600 drivers and I noticed that the used optocoupler on the DIR signal is much lower than the optocoupler on the STEP signal. I expect I need a delay of about 10usec to let the driver get the right direction when the pulse start.

Do you plan to support this parameter in the future?

Note: I think it could be done without using a new timer, just by using an interrupt on a compare of an existing timer.

Thanks in advance for your reply.

Hi, I was able to successfully build and upload the HEX file to the Bluepill. However, after I plugged in the USB cable to the computer, nothing happened. There was no new COM port that I could see. Am I missing something?

The Makefile included in the project is the one for building AVR Project. I've done a first port of that file. Additionnaliy, a linker script have to be included.

Please find included 2 txt files (remove txt extention) as a suggestion for Makefile and Linker script.

Makefile.txt
STM32F103C8T6.ld.txt

did not find stm32f103c8 chip in coide 2.0.6 (Build id: 20170117-2.0.6). Which version do you use? I suppose it have to be stm32f103c8t6 to work well.


my other projects in stm32f103c8t6 (the board is the same as yours) are opened and work.

Hello,

I have a few stm32f1 around but i am in doubt if them would perform really better then the avr

From your account i see that you made both the mega version then this. Which is your experience about? The more powerful stm32 outperform the tiny 8bit? Which would you suggest for a new design?

If you have any issues regarding this port, please post here instead go to main branch's ARM discussing.

Also attached prebuild in here. You can use serial port to load to your module.
stm32grbl.zip

I've always had strange errors in bCNC when zeroing X, Y or Z axis or pressing the stop button several times in a row. The errors only happen if "Hard limits" are enabled ($21=1). After some debugging I found that EXTI15_10_IRQHandler() in limits.c gets triggered although it should not. I think the problem is somehow related to USB connected to pins PA11/PA12 and the Y/Z limit switches connected to PB11/PB12. After changing the Y/Z limit switches to PA1/9 the problem is gone.

So maybe that's worth some more debugging ...

I've found a small bug resulting in a slightly different behaviour than the original GRBL.
In system.c (line 480) "sys_rt_exec_alarm |= (code);" has to be changed to "sys_rt_exec_alarm = (code);"

@usbcnc
Do you mind making this change and also my other findings (#29, #36, #38) to your GitHub repository ?
Otherwise they are not very useful ...

This still needs some more investigations: #39

Best regards,
lakeroe

Mapping direction pins to pins higher than 7 doesn't work.
The following changes will fix this:
planner.h, line 63
uint8_t direction_bits; --> PORTPINDEF direction_bits;
stepper.c, line 106
uint8_t direction_bits; --> PORTPINDEF direction_bits;

best regards
thkais

i progrom it in mdk ,but can't use usb ,thanks for ur work

Hi,

I try to solve this problem now for one and a half days. I designed my own CNC machine and homeing it is no problem. But when I start UGS it gives me an ALARM:PROBE but my Probe is not probing nor touching anything to close a circuit.

When I start probing (after homing, repositioning to my workpice and putting the axes to 0) I get a bunch of errors.

I tried different versions of UGS, tried to invert the probe pin. A pull down resistor is not needed (I read it in several forums but maybe I am mistaken?). I followed this tutorial.

I use an STM103 (source code) and no Arduino as a controller for grbl. When I put the Probing pin to Ground the error goes away and I can start probing.

Here are my settings:

$0 = 64    (Step pulse time, microseconds)
$1 = 0    (Step idle delay, milliseconds)
$2 = 7    (Step pulse invert, mask)
$3 = 7    (Step direction invert, mask)
$4 = 0    (Invert step enable pin, boolean)
$5 = 0    (Invert limit pins, boolean)
$6 = 0    (Invert probe pin, boolean)
$10 = 0    (Status report options, mask)
$11 = 0.010    (Junction deviation, millimeters)
$12 = 0.002    (Arc tolerance, millimeters)
$13 = 0    (Report in inches, boolean)
$20 = 0    (Soft limits enable, boolean)
$21 = 1    (Hard limits enable, boolean)
$22 = 1    (Homing cycle enable, boolean)
$23 = 0    (Homing direction invert, mask)
$24 = 25.000    (Homing locate feed rate, mm/min)
$25 = 500.000    (Homing search seek rate, mm/min)
$26 = 250    (Homing switch debounce delay, milliseconds)
$27 = 4.000    (Homing switch pull-off distance, millimeters)
$30 = 10    (Maximum spindle speed, RPM)
$31 = 0    (Minimum spindle speed, RPM)
$32 = 0    (Laser-mode enable, boolean)
$100 = 640.000    (X-axis travel resolution, step/mm)
$101 = 640.000    (Y-axis travel resolution, step/mm)
$102 = 640.000    (Z-axis travel resolution, step/mm)
$110 = 600.000    (X-axis maximum rate, mm/min)
$111 = 600.000    (Y-axis maximum rate, mm/min)
$112 = 600.000    (Z-axis maximum rate, mm/min)
$120 = 40.000    (X-axis acceleration, mm/sec^2)
$121 = 40.000    (Y-axis acceleration, mm/sec^2)
$122 = 40.000    (Z-axis acceleration, mm/sec^2)
$130 = 250.000    (X-axis maximum travel, millimeters)
$131 = 150.000    (Y-axis maximum travel, millimeters)
$132 = 90.000    (Z-axis maximum travel, millimeters)

MANY Thanks and have a nice day.

I've tried to build code from repository (using make), but build process fails because of missing file. Where I can find it? And, perhaps, it worth to include it in order to enable building without IDE. This is especially important taking into account that CooCox is not working under OS'es other than Windows.

If you press the reset button during the G4 delay (idle state), this will not stop the program execution.
motion-control.c

// Kill steppers only if in any motion state, i.e. cycle, actively holding, or homing.
// NOTE: If steppers are kept enabled via the step idle delay setting, this also keeps
// the steppers enabled by avoiding the go_idle call altogether, unless the motion state is
// violated, by which, all bets are off.
if ((sys.state & (STATE_CYCLE | STATE_HOMING | STATE_JOG)) ||
(sys.step_control & (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_SYS_MOTION))) {
if (sys.state == STATE_HOMING) {
if (!sys_rt_exec_alarm) {system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_RESET); }
} else { system_set_exec_alarm(EXEC_ALARM_ABORT_CYCLE); }
st_go_idle(); // Force kill steppers. Position has likely been lost.

}

Hello!
I've added additional axes.
The 4 axles work! 5 and 6 havn't checked yet.
So far, it has not done thorough testing (including limits, max step frec etc.).
I would like to clarify where the delay time (the frequency of updating the output STEP signals) is set (tune), because 4 axes output frequency will be lower than for 3 axis, and for 6 - more lower, right?
So, where can I change maximum step rate (sampling rate)?, for example, set the maximum output frequency for 4 axes two times lower (90kHz) than now for 3 axis (180kHz), to be sure that all operations will succeed.
One more question: whether it is necessary to expand any buffers, if so, which ones.
In the attachment, a project with modifications for 4 axes (without "grblwin" folder because of it size).
In the config.h (line 51) - // Define additional A, B and C axis

Sincerely, Yaroslav.
grbl-edge ABC.zip

Pins used for detecting limits on X,YZ trigger interrupts. The interrupts are linked to a specific NVIC_IRQChannel (EXTI15_10_IRQn ).
So all 3 pins have to be in the range 10 to 15.

This should be at least documented in cpu_map.h.

A similar issue exists for pins used for controls (range must be 5 to 9).

I found this issue when I had to redefine the pins used for step/dir/enable because I had to use 5 volt compliant pins for the stepper drivers I am using .

Link to the releases (on the home page) will redirect you to the original gnea/grbl releases - not to the releases of this project. It is quite misleading...

However, no releases in this project... :-)

Hex file or other compiled binary will be good as CooCox IDE is only for Windows. Linux users cannot compile this project simply.

Is there any way to add an IR sensor that can use one of the pins and to display the RPM of the spindle?
Thank you.

I tried to build project with CoIDE 2.06, since 2.x is now the main download.

stm32grbl11d.coproj needs to be adapted because Coide needs now complete device name : "STM32F103C8T6" instead of "STM32F103C8" for 1.x version .

Changes must be done at 2 places in the file, and needs to be edited BEFORE opening it with CoIDE.
Defines section needs also to be adated by ADDING (not replacing) a -DSTM32F103C8T6 .

Now the project builds.. but USB is not enumerated as serial port. I need to compare with a build done with 1.x.

My Sample project file is included, but needs further testing.

grbl-stm32.zip

Changes

1. 4th axis was added (tested)
2. grbl.h issue#36 (not tested)
3. main.c issue#38 (tested)
4. planner.h issue#41
5. probe.c uint16_t probe_invert_mask
6. serial.c, serial.h, usb_endp.c issue#46 now can use old and changed code by chooseing #define USB_CHANGED_DEBUG in serial.h (tested not in depth)
7. system.c issue#40
8. system.c EXTI_InitStructure.EXTI_Trigger is Rising_Falling instead of EXTI_Trigger_Falling (for NC and NO buttons. Need more tests)
9. stepper.c issue#41
10. stepper.c issue#49
11. stepper.c (config.h) NEW: STP_DRIVERS_ENABLE_DELAY (tested. see description in config.h)
12. stepper.c (config.h) issue#48 STEP_PULSE_DELAY now works (tested, but need more tests)
13. stepper.c issue#50 (tested)
14. system.c GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable, ENABLE); // to enable PA15, PB3, PB4 pins (tested)

LedBlink function in main() doens not seems to be called anywhere, so led stays off...

system.c
WORK (modified code):

void EXTI9_5_IRQHandler(void)
{
	EXTI_ClearITPendingBit(EXTI_Line5 | EXTI_Line6 | EXTI_Line7 | EXTI_Line8);
	uint8_t pin = system_control_get_state();
	if (pin)
	{
		if (bit_istrue(pin,CONTROL_PIN_INDEX_RESET))
		{
			mc_reset();
		}
		else if (bit_istrue(pin, CONTROL_PIN_INDEX_CYCLE_START))
		{
			bit_true(sys_rt_exec_state, EXEC_CYCLE_START);
		}
		else if (bit_istrue(pin, CONTROL_PIN_INDEX_FEED_HOLD))
		{
			bit_true(sys_rt_exec_state, EXEC_FEED_HOLD);
		}
#ifdef ENABLE_SAFETY_DOOR_INPUT_PIN
		else if (bit_istrue(pin, CONTROL_PIN_INDEX_SAFETY_DOOR))
		{
			bit_true(sys_rt_exec_state, EXEC_SAFETY_DOOR);
		}
#endif
		NVIC_ClearPendingIRQ(EXTI9_5_IRQn);
	}
}

doesn't work (The original version):

void EXTI9_5_IRQHandler(void)
{
	uint8_t pin = system_control_get_state();
	if (pin) 
	{ 
		if (bit_istrue(pin,CONTROL_PIN_INDEX_RESET)) 
		{
			mc_reset();
		}
		else if (bit_istrue(pin, CONTROL_PIN_INDEX_CYCLE_START))
		{
			bit_true(sys_rt_exec_state, EXEC_CYCLE_START);
		}
#ifndef ENABLE_SAFETY_DOOR_INPUT_PIN
		else if (bit_istrue(pin, CONTROL_PIN_INDEX_FEED_HOLD))
		{
			bit_true(sys_rt_exec_state, EXEC_FEED_HOLD);
		}
#else
		else if (bit_istrue(pin, CONTROL_PIN_INDEX_SAFETY_DOOR))
		{
			bit_true(sys_rt_exec_state, EXEC_SAFETY_DOOR);
		}
#endif
		NVIC_ClearPendingIRQ(EXTI9_5_IRQn);
}
}

In my application the G-Code "G4 P3" did not work correctly.
I think the problem is caused by the _delay_ms function in main.c.
If I change line 196 from
SysTick->LOAD = (u32)72000000 / 8000; // Loading time

to
SysTick->LOAD = (u32)72000000 / 8000 * x; // Loading time

everything works fine.

Best regards,
lakeroe

To enable PB3, PB4 and PA15 pins you have to disable JTAG:
GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable, ENABLE);