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Boot own code from sdcard -  whats missing please

Question asked by John Ballance on Oct 16, 2013
Latest reply on Oct 17, 2013 by John Ballance

Hi

I am attempting to load a custom OS from SDcard. I have a SDCard boot loader that uses the IVT etc to initialise the dram, then load a kernel at 0x17800000 in dram.

 

If I paste a linux kernel on the end of this it runs, so I know ram is set up and the kernel is put in the right place to execute.

 

I then put my minimal kernel in place of the linux kernel and see nothing.

 

I am attempting to send something via the serial port but must be missing something.

What I do is:

1: set AIPS1_MPR0to7 and 8to15 to 0x77777777 to turn on unbuffered write access to all masters. the same for AIPS2

2: set all the AIPSx_OPACR registers to 0 to unbuffered un priveledged write to all peripherals

3: set pads PAD_CTL for _EIM_D19/20 and CSI0_DAT10/11 to 0x1b0b0  (the 4 pins in use

4: set MUX_CTL for CSI0_DAT10/11 to 3 (alt_3)

5: set UART1_IPP_UART_RXD and UART_RTS_B to 1

6: clear bottom 6 bits of CCM_CSCDR1 to set uartpodf divider to 1

7: set CCM_CCGR5 bits 24-27 to enable uart clocks

then

8: usual uart setup, with known working routines.

What have I missed???  I cannot get any toggling of serial output pin

 

THanks in hope

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