i.MX RT 1024 without 32kHz crystal

[balbet]

Hi,

We assembled some protos with the i.MX RT 1024 and everything worked fine. Then we realised the RTC of the iMX RT consumes a lot, so we had to add an external RTC IC and then we moved the crystal in there. So, the only change from the i.MX RT IC was that now we don't have the 32kHz crystal.

In that new situation, we find that we can't flash the memory anymore in empty ICs. If then we solder the crystal externally, we can flash the memory correctly, and once it is programmed at least one time, we can desolder the crystal and it works fine forever. The thing is we don't need that crystal, and it seems a waste of money to have to solder a crystal only to be able to program the flash memory for the first time.

Is this a known issue?

Thanks!

[kerryzhou · Accepted solution]

Hi @balbet ,

  I totally understand you!

   But, please note, the 32K not only used for the RTC, it also used for many other IPs, eg:

1. SNVSMIX. The RTC count will not so accurate.--ignore, as you add external RTC.
2. CCM. May impact lower power mode entry
3. SRC. May impact reset timing
4. csu.ap_ckil_clk // Secured Low frequency clock input for the Emergency Reset Counter
The csu_alarm_out0 output from csu_reg is passed into this module and depending on counter value, is given out after a specified amount of time
5. ewm.ckil_clk
6. gpt1.ipg_clk_32k
7. gpt2.ipg_clk_32k
8. kpp.ipg_clk_32k
9. tsc_dig.lp_clk
10. usb.ipg_clk_32k
11. usdhc1.ipg_clk_32khz
12. usdhc2.ipg_clk_32khz
13. wdog1.ipg_clk_32k
14. wdog2.ipg_clk_32k
15. wdog3.int_clk

So, from our internal R&D team, we still recommend you add the external 32k crystal in the real product.

Wish it helps you!

Best Regards,

Kerry

[balbet]

Hi Kerry,

Ok, many thanks for your detailed explanation! We checked the fuses and we've seen nothing related with the 32k clock, but is there any chance (for example using some reserved fuses) to use the internal oscillator instead of the crystal for such a purposes? We'd like to prevent a new proto redesign/assembly/etc...

Thanks!

[kerryzhou]

Hi @balbet ,

   Internal oscillator is not accurate, we don't recommend you use the internal oscillator in the product, it is normally for the boot.

  In the product, we still recommend you add the external 32k crystal, thanks.

Best Regards,

Kerry