When "boot0-3 pin is low" and the ATK states "Connection error. Please reset the board and make sure the board in bootstrap mode" - often this means the i.MX27 does not start.
Below are general recommendation regarding boot issues :
I.
Please check in 32KHz input clock is present and proper (voltage level, off-duty factor).
II.
Please pay special attention on PLLs supply (FPMVDD, MPLLVDD,UPLLVDD) - if they
meet Hardware Specs in the MX27 Datasheet are have no ripples.
III.
Is power up sequence fully correct ?
Especially - if reset signal is active for sufficient time, while power voltages
are not stable.
Let me remind, the i.MX27 Datasheet takes special attention on FuseVDD and QVDD
relations :
"It is important that the applications processor power supplies be powered-up in
a certain order to avoid unintentional fuse blown. QVDD should be powered up
before FUSEVDD."
The i.MX27 Datasheet also provides two variants :
"The recommended order is:
1. QVDD(1.5 V)
2. FUSEVDD (1.8 V), NVDD (1.8/2.775 V), and Analog Supplies (2.775 V).
or
1. QVDD (1.5 V), NVDD (1.8/2.775 V), and Analog Supplies (2.775 V).
2. FUSEVDD (1.8 V)."
IV.
Please check if POR signal is asserted while all power supply voltages are not stable.
Perhaps it makes sense to prolong POR. To be latched / detected, minimal POR
duration is 4 x 1 / 32KHz, But in the same time, it is general rule, that POR
must be asserted while
- input clocks are not proper and stable ;
- supply voltages are not proper and stable.
So, minimal POR duration is application / design dependent.
Practically POR of 1-2 sec should be enough for most cases.
