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[Spyy]

Hi,

i have really a problem here. The BT81x should run default with 60 Mhz core clock an the new one with 72 MHz when i write:
EVE_cmdWrite(EVE_CLKSEL, 0x46); /* set clock to 72 MHz */

Then i do this:
EVE_memWrite32(REG_FREQUENCY, 72000000); to set it correct

I am setting up the chip and then check the speed with:
   // Write the EVE stats:
   uint32_t eveClockOld = EVE_memRead32(REG_CLOCK);
   delay(1000);
   uint32_t eveClockNew = EVE_memRead32(REG_CLOCK);
   Serial.print("EVE clock: ");
   Serial.println(eveClockNew - eveClockOld);
   delay(1000);
   uint32_t eveFramesOld = EVE_memRead32(REG_FRAMES);
   delay(1000);
   uint32_t eveFramesNew = EVE_memRead32(REG_FRAMES);
   Serial.print("EVE frames: ");
   Serial.println(eveFramesNew - eveFramesOld);

With the values set to:
EVE_cmdWrite(EVE_CLKSEL, 0x46)
EVE_cmd_pclkfreq(50500000L, 0)
EVE_memWrite8(REG_PCLK, 0x01)

i get this:
EVE PCLK Frequency: 50000000 => OK
EVE clock: 34668795 => would expect 72000000 or something here (looks like approx half of 72000000 Hz)
EVE frames: 85

With nothing written to EVE_CLKSEL (which should be default => 60 Mhz) I get:
EVE PCLK Frequency: 50000000 => OK
EVE clock: 28909452 => would expect 60000000 or something here (looks like approx half of 60000000 Hz)
EVE frames: 85

I am using no external crystal with the setting EVE_cmdWrite(EVE_CLKINT,0);   /* setup EVE for internal clock */ set.

So my question is what can be the reason for this or do i missed/messed up here something ?

Thank you for your help.

Torsten

[BRT Community]

Hello,

Thank you for your question.

The REG_CLOCK register holds a value for the number of clock cycles since the last chip reset, and should not be used for an indication of the PCLK rate being used by the IC.

Please see section 4.5 of the datasheet for an explanation no how to se the PLCK frequency:
https://brtchip.com/wp-content/uploads/Support/Documentation/Datasheets/ICs/EVE/DS_BT817_8.pdf

Best Regards,
BRT Community

[Rudolph]

I just did a little experiment and tried to init a display with a BT817 that has a crystal to use the internal oscillator.
And it failed, it runs much slower, starts to flicker and the displayed frequency from reading REG_CLOCK twice with a delay of 1s in between dropped to 38MHz.

So I checked the datasheet and learned that apparently the "Internal relaxation oscillator clock" and the option "External 12MHz square wave clock" have been removed from the BT817 / BT818.
The chapter 4.2.1 "Clock Source" of the BT817 / BT818 lists an external crystal as the only option.

Chapter 4.2.3 "Clock Enable" has the internal clock removed.

Chapter 4.2.4 "Clock Frequency" has a whole paragraph removed.

Chapter 4.9.4 might have been overlooked during editing as it still says:
"Upon receiving the SPI ACTIVE command (or CLKEXT followed by SPI ACTIVE command if external clock source is used)"

And finally CLKINT has been removed from table 4-4 on page 15.

Ok, I also saw that the experiment was not valid in the first place since my module has a crystal populated and according to the BT815 / BT816 datasheet X1/Clk needs to be tied to GND for the internal relaxiation oscillator.

But it looks like the issue here is that running BT817 / BT818 without a crystal or resonator is no longer an option.