Lime2 : i suspect a hardware default

[Jegeva]

Hey guys & gals,

Just bought an a20 lime 2 and it hangs on :
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U-Boot 2018.05-armbian (Oct 26 2018 - 17:47:17 +0200) Allwinner Technology

CPU:   Allwinner A20 (SUN7I)
Model: Olimex A20-OLinuXino-LIME2-eMMC
I2C:   ready
DRAM:  1 GiB
MMC:   SUNXI SD/MMC: 0, SUNXI SD/MMC: 1
Loading Environment from EXT4... ** File not found /boot/boot.env **

** Unable to read "/boot/boot.env" from mmc0:1 **
Failed (-5)
HDMI connected: Setting up a 1920x1080 hdmi console (overscan 0x0)
Error: no valid bmp image at 66000000
In:    serial
Out:   vga
Err:   vga
Allwinner mUSB OTG (Peripheral)
SCSI:  SATA link 0 timeout.
AHCI 0001.0100 32 slots 1 ports 3 Gbps 0x1 impl SATA mode
flags: ncq stag pm led clo only pmp pio slum part ccc apst
Net:   eth0: ethernet@01c50000
Warning: usb_ether using MAC address from ROM
, eth1: usb_ether
230454 bytes read in 79 ms (2.8 MiB/s)
starting USB...
USB0:   
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for both the armbian official release (Armbian_5.65_Lime2_Debian_stretch_next_4.14.78 at the time of writing, the one on the serial output used as an example) and A20-lime2_mainline_uboot_sunxi_kernel_3.4.103_jessie_eMMC_rel_16 from the wiki page.

it is powered from a 5V/2A wall adapter on the usb OTG port.

Any ideas ?

Jegeva

[JohnS]

If you don't have eMMC but only NAND then one or both will not work - at least so I gather from the wiki page.

You do need a suitable image, not one that is close.

John

[Jegeva]

This is only happening when powering via the OTG usb port, it boots when powered from the barrel jack.

Any idea why the OTG is blocking ?

cheers

[LubOlimex]

I suspect that the problem is the powering. Powering the board via the USB is not recommended. Even if you have externally powered USB port, the power input via the USB power line is limited. If you don't care about the details, please skip the next two paragraphs.

The USB current is limited typically to 500mA (and 900mA is the absolute maximum), no matter how powerful your power supply is, the AXP209 power management unit inside the board would limit the current available after it. There are separate inputs (power lines) for the power supply from the USB and the external power supply. The 5V USB power supply goes to VBUS pin of the power management chip AXP209, while 5V external power supply goes to ACIN pin of the same AXP209. There are different power input lines for a couple of reasons.

If you look at the table in "5. Electrical Characteristics" on page 6 of the datasheet of AXP209 (here: http://dl.linux-sunxi.org/AXP/AXP209_Datasheet_v1.0en.pdf) - you would notice that the absolute maximum current available from AXP209 when power supply is supplied on VBUS is 900mA (no matter how much current you have available, AXP209 would output no more than 900mA). Of course, probably more than half of this current is required for the board itself (without anything extra attached)! In the same table you also see when the power is instead provided on the ACIN pin of AXP209 (e.g. when powered via the power jack) - the typical current available is 2500mA!

[baba]

I suspect that the problem is the powering. Powering the board via the USB is not recommended.

Same here:
I did not succeed to boot an image while being powered through USB.

Even if you have externally powered USB port, the power input via the USB power line is limited. If you don't care about the details, please skip the next two paragraphs.

The USB current is limited typically to 500mA (and 900mA is the absolute maximum)

Thank you for the details!

Is 900mA enough to power the board (with no externals) and boot one of olimex official images?

If not, maybe the doc should state "Powering the board via the USB is not possible" instead of  "Powering the board via the USB is not recommended."

Or maybe the doc could clarify that powering the board through OTG is only useful when using a battery? (Which is a nice feature!)

[JohnS]

Or perhaps it should be "Powering the board via the USB is not recommended unless you make sure your operating system does not power up too many subsystems."  (It may also need to say that some official images are like that - right?)

That way it will allow for the various changes being made with such as Linux for Allwinner.

I hope that a stripped-down DT would cause lower power to be used.

A battery won't last long at anything like 900mA...

John