Debugging a warp board that won’t turn on

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While working with warp it is possible that you accidentally put the board into a state where it will not boot.

There are a variety of reasons this can happen such as clobbering the bootloader, setting a bad boot parameter, or the battery or charger input voltages being too low.

Whatever the case, it is very likely that your hardware is fine.

Following these steps may help you determine the cause of the issue and get your board back up and running.
1 – First, set up your system to a known configuration, attached to an interposer board.
With both USB and power disconnected, set up interposer board jumpers as follows:
ALT CHARGE SOURCE – Not jumpered/Open Circuit
USB DEBUG VBUS – Jumpered/Closed Circuit
J8 – Not jumpered/Open Circuit
J9 – Jumpered/Closed Circuit
BM0 – Not jumpered/Open Circuit

2. Connect CONSOLE/DEBUG micro USB – two new tty devices should show up

3. Open two serial terminal connections, one to each of the new tty devices at 115200bps, 8 data bits, 1 stop bit, no parity, no flow control

4. Press PUSH BTN1 and hold for about 1-2 seconds. There is no harm in holding longer, but it only takes a momentary press.
When powered only from the external power inputs, the power button is necessary to turn on the warp board.
Did the board start? Did uboot start sending console output to one of your serial terminals?
If yes, then great, you’re back up and running. If not, continue.

5. Remove USB DEBUG VBUS and J9 jumpers. All headers on board should be open circuit. The two serial consoles should still be open and ready to receive data from warp.

6. Connect a second micro USB cable to the warp. Did the board start? Did uboot start sending console output to one of your serial terminals?
If yes, then great. Problem may be that the input voltage to the vbat connection is below a turn on threshold. There is some additional debugging we could do at this point to track down the specific issue, but your board is working and you should be mostly back up and running
If not, continue.

7. Now we will see if we can put the board into serial bootloader mode and reimage the warp board.

8. Disconnect the micro USB cable that is connected to the warp board. Leave the CONSOLE/DEBUG micro USB cable connected.

9. Add a jumper to the BM0 header.
BM0 – Jumpered/Closed Circuit

10. Reconnect second micro USB cable to the warp. Does a new USB HID device appear on your host or VM? Does the computer make a USB device connected sound?
If yes, then we can reflash the board with imx_usb or the nxp manufacturing tool.

There are instructions included board documentation for how to do this, so I’ll leave that post for another day.

Easy OS upgrades with SWUpdate

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As we have shown at ELC2017, we integrated an easy way for warp_0x01 users to upgrade the OS installed in their boards.

Thanks to the nice features provided by SWUpdate and the integration work that we have done in our meta-warpx Yocto layer we are now able to provide straightforward complete OS upgrades in a single file through a simple web interface.

> SWUpdate web interface

WARNING: Keep in mind the procedure wipes all the data in the storage of the warp_0x01 and flashes the latest version of the Linux distribution we built using Yocto.


SWUpdate operates in the following way: a client running on the target (the warp_0x01) obtains an .swu file from the host (your PC) which is then unpacked and interpreted to flash the new OS in the storage (the eMMC).

The installation of the SWUpdate client is done by doing a raw copy of our all-in-one SWUpdate standalone OS image to the warp_0x01 storage using the U-Boot USB Mass Storage feature to export the eMMC as a USB storage. This operation thus requires:

  • a working U-Boot in the warp_0x01 board with serial console access. If you own an interposer board and haven’t intentionally hacked up U-Boot in your board this requirement is already satisfied
  • a tool for raw copy (dd in Linux and Mac OS, USB Image Tool or Win32 Disk Imager in Windows)

The transfer of the file to the target is done via a web interface exposed by SWUpdate on a fixed IP of an USB Gadget Ethernet interface. To reach the fixed IP of the target, the host computer should support RNDIS USB Ethernet: most Linux distributions include the driver out of the box, while Windows and Mac OS might require manual installation of appropriate driver, depending on the version.

We’ll not enter in the details of using raw copy tools other than dd or how to install RNDIS USB Ethernet drivers, as there are plenty of howtos available on the internet that cover those topics.

SWUpdate client installation

As anticipated, the first step to update the board is to install the SWUpdate client with the SWUpdate standalone OS image we provide. Download the file swupdate-standalone-os.img and follow instructions below.

U-Boot USB Mass Storage setup

To expose warp_0x01 eMMC storage to the host as a USB Mass Storage:

  1. open the serial console on the host computer
  2. power up the warp_0x01
  3. interrupt U-Boot autoboot countdown on the serial console
  4. export the eMMC to the host with the following command
    => ums 0 mmc 0
    UMS: LUN 0, dev 0, hwpart 0, sector 0x0, count 0x748000
  5. a 4GB storage device should appear on the host

Flash of the SWUpdate standalone OS image

On the host identify the warp_0x01 4GB storage device and flash the swupdate-standalone-os.img. As an example procedure on Linux should be as follows:

# dd if=swupdate-standalone-os.img of=/dev/disk/by-id/usb-Linux_UMS_disk_0-0\:0 conv=fsync
51824+1 records in
51824+1 records out
26534293 bytes (27 MB, 25 MiB) copied, 26.748 s, 992 kB/s

Now the SWUpdate standalone OS image is flashed and ready to be booted.

Boot SWUpdate standalone OS image

Return to U-Boot and interrupt the USB Mass Storage mode with Ctrl+C.
At the U-Boot prompt enter the following commands to boot the SWUpdate standalone OS image:

=> mmc read ${initrd_addr} 0x2000 0xAA80

MMC read: dev # 0, block # 8192, count 43648 ... 43648 blocks read: OK
=> setenv initrd_high ${initrd_addr}
=> bootm ${initrd_addr}
## Booting kernel from Legacy Image at 83800000 ...
   Image Name:   Multi-file image
   Image Type:   ARM Linux Multi-File Image (gzip compressed)
   Data Size:    22339925 Bytes = 21.3 MiB
   Load Address: 80008000
   Entry Point:  80008000
      Image 0: 5898480 Bytes = 5.6 MiB
      Image 1: 16408006 Bytes = 15.6 MiB
      Image 2: 33421 Bytes = 32.6 KiB
   Verifying Checksum ... OK
## Loading init Ramdisk from multi component Legacy Image at 83800000 ...
## Flattened Device Tree from multi component Image at 83800000
   Booting using the fdt at 0x84d45f08
   Uncompressing Multi-File Image ... OK
   Loading Ramdisk to 8285a000, end 837ffdc6 ... OK
   Using Device Tree in place at 84d45f08, end 84d51194

Starting kernel ...

Booting Linux on physical CPU 0x0
Linux version 4.1.15-1.0.0_ga+g1eb0314 (yocto@ubuntu-yocto) (gcc version 5.3.0 (GCC) ) #1 SMP PREEMPT
 Wed Mar 15 17:10:43 CET 2017

The SWUpdate standalone OS will now start and be ready in a bunch of seconds.

Firmware update file transfer and deploy

Now that the SWUpdate client is up and running on the warp_0x01 we need to setup the host to connect and reach the webpage to upload the .swu firmware update file.

Setup the RNDIS USB Ethernet interface

As the warp_0x01 USB Ethernet interface is already setup with the fixed IP (netmask all that is needed is to set a fixed IP on the USB Ethernet device on the host on the same network. This is a Linux example to do so:

# ip link set dev usb0 up
# ip addr add dev usb0
# ping -c 1
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.466 ms

--- ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.466/0.466/0.466/0.000 ms

Upload firmware update file

Now that everything is set up, updating the OS on the warp_0x01 should be straightforward: opening a browser on the URL will bring you to the SWUpdate web interface.

Download the most recent .swu firmware update file provided on the > resources download area and upload it to the warp_0x01 via the web interface. Here’s the quick link to warpx_1.1.0.swu shown in action below.

> SWUpdate web interface showing progress of the OS upgrade

When the web interface reports “SWUPDATE successful !” in the Status Messages of the web interface the OS is successfully upgraded, and you can boot it just by pressing the “Reboot Device” button!

Whenever you want to upgrade to a newer version, you just need to go back to the “Boot SWUpdate standalone OS image” section and follow the instruction from there on!


We hope that the work we’ve done will help you with the task of keeping your warp_0x01 up-to-date.

We plan to make some improvements in the future to upgrade the installed version of U-Boot too and allow to easily switch from the regular OS to the SWUpdate standalone OS without having to enter commands to the U-Boot prompt. So if you have any feedback or you need a helping hand, please reach out to us in the mailing list!

Warp | Yocto Linux – Accessing the serial console

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We’ve put together various HOWTO videos that should help you get to the serial console on different OSes with different configurations, (Warp standalone or via the Interposer board). We’ve covered Linux, Mac and Windows.

You can find the bundle of videos over on our YouTube channel.  Otherwise, here are direct links for each:

Serial Console, standalone Warp on Linux

Serial Console, standalone Warp on MacOS

Serial Console on Warp via Interposer on MacOS

Serial Console on Warp via Interposer on Linux

Serial Console on Warp via Interposer on Windows

Warp | Yocto Linux – Connect to WiFi Network

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To get warp connected to the Internet quickly, the Yocto Linux release for warp conveniently has a shell script: /home/root/wifi_connect, which enables you to get connected to a nearby WiFi network.

You may have to set the execute bit on this file to be able to run it as some earlier releases of Yocto Linux for Warp did not have execute permissions on the file. You can run:

chmod 750 /home/root/wifi_connect

to ensure that this is set correctly.

The wifi_connect script takes two arguments as input.
Argument #1: WIFI-NET
Argument #2: PASSWORD

For example:

/home/root/wifi_connect Starbucks pass1234

If you’d like to watch a YouTube video on this topic, see here: Warp – Yocto Linux – Connect to a WiFi Network

If you do not see the wifi_connect script under /home/root of your Warp, you can make the wifi_connect script using vi and the command line to include the following contents:

ip link set wlan0 up
iw dev wlan0 scan
mkdir -p /etc/wpa_supplicant/
wpa_passphrase $1 $2 >/etc/wpa_supplicant/file.conf
wpa_supplicant -B -iwlan0 -Dnl80211 -c/etc/wpa_supplicant/file.conf
iw dev wlan0 link
udhcpc -i wlan0

Connecting your MAC to the warp serial console.

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In this post we will cover how to connect your Mac to the warp using the serial console if your warp is programmed with Yocto.

There are two possible configurations:

  1. you have just the warp
  2. you have the warp docked to the interposer board.

In the case that you have only the warp board, the serial console will be accessible because the multi_gadget kernel module is loaded at boot time. Using the same MicroUSB cable that powers the board, after few seconds you will find in your Mac a device like:


Next, you can use a terminal emulation program like minicom to open the serial console.

If you have only the warp, the terminal does not provide output until the module has been loaded. This means that you will not be able to access the boot loader stage.

In the case you have also the interposer board, just connect a MicroUSB to the “CONSOLE DEBUG” port.

After connecting, your Mac will show a device like:


where xx is a two digit number that may vary depending on the dynamic device name allocation.

Having the interposer allows you to have access also to the U-Boot stage.

Just use a terminal emulation program like minicom to open such device.

Note: The warp board must also be powered on. While plugged into the interposer board, the warp does not require it’s own Micro USB connection. The interposer provides adequate power for both itself and the warp from a single Micro USB connection on the Console/Debug port. Ensure that the warp is powered on by pressing the “PUSH BTN 1 (PMIC PWR)” button on the interposer.