Software » Campo » Biwak

Clean up all the timing calculation garbage.
The values should be determined only by the periphery clock and bus Speed.

This has to be done for FDCAN and classic CAN.

Check if CFdCan and CCan can be merged. Filter is a little bit different. There are already different HAL-implementations for Classic-CAN.

Fuer 13/2: prescaler=Clock/speed/16; (Clock/speed)%16 muss 0 sein
48Mhz, 125Kbit, prescaler: 24
48Mhz, 500Kbit, prescaler: 6
8Mhz, 500Kbit, prescaler: 1

Bei hohen raten und geringem Takt funktioniert 13/2 nicht mehr

Fuer 10/1; prescaler=Clock/speed/12; (Clock/speed)%12 muss 0 sein
48Mhz, 2000Kbit, prescaler: 2

Fuer 6/1; prescaler=Clock/speed/8; (Clock/speed)%8 muss 0 sein
16Mhz, 2000Kbit, prescaler: 2

divider=1+(SEG1+SEG2)

<pre><code class="cpp">
struct SConfigs
{
char SEG1;
char SEG2;
} configs[]=
{
{13,2},
{10,1},
{8,1},
{6,1},
};

int getConfig(speed)
{
for(int i1=0; i1<sizeof(configs)/sizeof(configs[0]); i1++)
{
if( (HAL_RCC_CANClock /getBitRate(speed) ) % (configs[i1].SEG1 + configs[i1].SEG2 + 1) ) == 0 )
{
return(i1);
}
}
return(-1);
}

config=getConfig(enum);
lAssert( (config>=0) );
</code></pre>

<pre><code class="cpp">
bool getConfig(clock, speed, &seg1, &seg2, &preescaler)
{
seg1=13; seg2=2
// Because prescaler=clock/speed/divider we need neet an divider that produces is an integer.
// Don't waste much time; only check these combinations: { {13,2}, {10,1}, {8,1}, {6,1} }, hopefully the first one fits
while(seg1>=6)
{
int divider=seg1+seg2+1;
if( (clock /getBitRate(speed) ) % divider ) == 0 )
{
prescaler=clock/speed/divider;
return(true);
}
if(seg2>=2)
{seg2--; seg1--;}
seg1-=2;
}
return(false);
}

</code></pre>

Specified: 1Mbit, 500kBit, 250kBit, 125kBit, 50kBit, 20kBit, 10kBit, 5kBit

<pre><code class="cpp">
enum {
e1MBit = 1,
e500KBit = 2,
e250KBit = 4,
e125KBit = 8,
e50KBit = 20,
e20KBit = 50,
e10KBit = 100,
e5KBit = 200,
}
int getBitRate(enum)
{
return( (1000/enum) * 1000 );
}
</code></pre>

Speed = (1000/enum)*1000

The clock tree is created in the libstm at the moment.
There can be aliases in "stm32/rcc.h" for each family.
<pre><code class="cpp">
uint32_t HAL_RCC_GetCANFreq(void) asm("HAL_RCC_GetPCLK1Freq");
</code></pre>