The WeIO hardware module is composed by the following elements :
- A Wireless SoC Module (Carambola2) that acts as the system core.
- A coprocessor (NXP LPC11U24) which is used to assure the real-time aspects of the system and exposes GPIO, PWM, I2C, UART, SPI and ADC.
- An FTDI chip (FT232-RQ), used for the debug console
- A USB Hub (Microchp USB2640), used to extend the USB ports of the board and providing a SD card interface
- An I2C temperature sensor (LM75)
- An RGB LED
- Header with all the availables IOs
The complete schematic and BOM can be found on Github
Datasheet
Useful links
The Wireless SoC Module is a Carambola2 module made by 8devices.
It is build around an Qualcomm Atheros AR9331. The AR9331 is MIPS 24K MCU, running at 400MHz. The Carambola2 module contains 16MB of flash and 64MB of RAM, and is Wifi 802.11b/g/n compliant.
The base system is based on OpenWRT, a Linux distribution specifically made for embedded devices.
No GPIO exposed on the pin-headers come from this module. First, there's not enough GPIOs available on the Carambola2 module to create a complex application. The second point is that these GPIOs are only 2V55 tolerent, which makes them vulnerable during the development process. The third reason is that OpenWRT is not a real-time system, making it difficult to create a project in which timing constraints are important, which is mostly the case when dealing with hardware sensors or actuators.
That's the reason why a co-processor has been added.
Even if the GPIO exposed on the pin-headers come from the co-processor, the following board components are wired directly on the Carambola2 module :
- AP Mode switch on GPIO20 (Carambola2 module, pin 4)
- SOFT RESET switch on GPIO15 (Carambola2 module, pin 37)
- STA LED on LED5 (Carambola2 module, pin 36)
- AP LED on LED1 (Carambola2 module, pin 40)
- LM75 sensor on I2C : SDA on GPIO18 and SCL on GPIO19 (Carambola2 module, pins 6 and 5)
A shell is always available via the COM port when the board is powered through USB. The communication configuration is : 115200 bauds 8N1 (8 bits, no parity, 1 stop bit)
The power consumption of the Carambola2 module is not precisely known and is hard to determines. Some hints can be found here. This consumption will highly depends of the Wireless state.
As seen above (Wireless SoC module), the co-processor aims to provide robust and versatile GPIOs as well as assuring real-time exigences. In adition, the co-processor provides hardware modules such as PWM, ADC, SPI, I2C and UART.
The co-processor is an ARM Cortex-M0 32 bit MCU LPC11u24 from NXP, running at 48MHz.
The communication between the co-processor and the wireless module is made through USB. The co-processor implement a CDC interface to assure the communication.
A protocol, SFP (acronym of Simple Function Protocol) is used to send commands and get status back.
The electrical characteristics of the LPC11u24 can be found in the LPC11u2x datasheet
Here's a short summary of the most important characteristics :
GPIO
- Vi : Input voltage : 5V
- Vo : Output voltage : Vdd (3V3)
- Ioh : Output current : 4mA (Vdd-0.4V); 16mA (Vdd-1V)
ADC
- Via : Analog input voltage : Vdd (3V3)
- Cia : Analog input capacitance : 1pF max
- Ri : Input resistance : 2.5MOhm max
Up to two power modules can be plugged into a WeIO board, offering 16 outputs for each module. Each output can drive actuators consuming up to 50V and 500mA.
Connect the desired power supply to the +V and GND pins of the module. Then connect each of the output pins to one pin (the + one if available) of each of your actuators, and the other pin of the actuator to the common GND of the module.
Notice that the module is a current amplifier, so it will work directly with motors, lamps or other « continuous » actuators, or relays. In order to dim LEDs, it is necessary to create software PWM, or BCM or to use the PWM outputs of the WeIO (with an optional Darlington array if required by the power consumption), or a SPI LED driver (such as this one), which are actually more appropriate techniques.
A good place to start using the powerModule is the powerModule example from the actuators folders.
Technical description of the power module: The Power Module is composed of two 8 bit shift registers driving 2 arrays of 8 Darlington transistors.. See more on the power module’s repository.
Even if the flash space on WeIO is sufficient for most applications, when new python packages must be installed, or when the applications assets are important, the flash space available can fast become a problem.
To solve this problem, WeIO version 1.2 (and above) can be extended to a SD Card. This allow to increase the flash space from few megabytes to several gigabytes, depending of the SD card capacity.
Obviously, once the system is extended, the SD card must always stay plugged. Without it, the system will not boot anymore. Moreover, the future system updates will squash it and you will need to extend your system again.
N.B. you can read more about OpenWrt extroot feature here: http://wiki.openwrt.org/doc/howto/extroot
Before trying to extend your system, be sure to be able to connect to the board via the debug console.
For Linux and OSX, this can be done with screen :
screen /dev/ttyUSBx 115200 8N1 under Linux systems, or screen /dev/tty.usbxxxxxx 115200 8N1 under OSX.
On Windows system, PuTTY is known to work well.
You also need an empty SD Card. If the SD Card is not empty, it will be erased during the processus. The filesystem in which the SD Card is formatted is not important.
To extend the root filesystem, it's strongly recommended to insert only the SD Card. All other external storage devices (USB HDD or USB Flash) must be disconnected of WeIO.
Via the debug console, connect to the board (and if needed, press enter) : the banner should be displayed :
## ## ######## #### #######
## ## ## ## ## ## ##
## ## ## ## ## ## ##
## ## ## ###### ## ## ##
## ## ## ## ## ## ##
## ## ## ## ## ## ##
### ### ######## #### #######
WEIO Web Of Things Platform
Copyright (C) 2013-2015 Nodesign.net,
Uros PETREVSKI, Drasko DRASKOVIC
All rights reserved
root@WEIO:/#
By default, removable devices are automatically mounted under /weioUser/. To control that your SD Card is correctly detected and mounted, you can type the command :
root@WEIO:/# df
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 3904 312 3592 8% /
/dev/root 11264 11264 0 100% /rom
tmpfs 30812 276 30536 1% /tmp
/dev/mtdblock5 3904 312 3592 8% /overlay
overlayfs:/overlay 3904 312 3592 8% /
tmpfs 512 0 512 0% /dev
/dev/sda1 3863720 8036 3639700 0% /weioUser/sd
The SD Card (/dev/sda1) is currently mounted on weioUser/sd.
The process that automatically check for removable device and mount them must be stopped :
root@WEIO:/# /etc/init.d/usd stop
And the SD Card can be unmounted :
root@WEIO:/# umount /weioUser/sd/
root@WEIO:/# rm -r /weioUser/sd # Manually remove the mountpoint
At this point, the SD Card can be prepared. The first step is to format it :
root@WEIO:/# mkfs.ext4 -F /dev/sda1
Once formatted, the SD Card can be mounted under /mnt
root@WEIO:/# mount /dev/sda1 /mnt/
Now we can setup the system to use the SD Card :
block detect > /etc/config/fstab
You'll now have to manually edit /etc/config/fstab, with nano or vi :
root@WEIO:/# vi /etc/config/fstab
The file will looks like :
config 'global'
option anon_swap '0'
option anon_mount '0'
option auto_swap '1'
option auto_mount '1'
option delay_root '5'
option check_fs '0'
config 'mount'
option target '/mnt/sda1'
option uuid '0824a446-69a1-405a-b856-b276102fa6db'
option enabled '0'
The SD Card must be mounted on /overlay during the boot process. To do that, the file must be edited that way :
config 'global'
option anon_swap '0'
option anon_mount '0'
option auto_swap '1'
option auto_mount '1'
option delay_root '5'
option check_fs '0'
config 'mount'
option target '/overlay'
option uuid '0824a446-69a1-405a-b856-b276102fa6db'
option enabled '1'
Then, save the file.
Now, the content of /overlay must be copied on the SD Card :
root@WEIO:/# tar -C /overlay -cvf - . | tar -C /mnt -xf -
And finally, the SD Card can be unmounted :
root@WEIO:/# umount /mnt/
The system is now ready. You can reboot the system :
root@WEIO:/# reboot
When the system has finished to boot, you can check that the system has been extended :
root@WEIO:/# df -h
Filesystem Size Used Available Use% Mounted on
rootfs 3.7G 7.8M 3.5G 0% /
/dev/root 11.0M 11.0M 0 100% /rom
tmpfs 30.1M 32.0K 30.1M 0% /tmp
/dev/sda1 3.7G 7.8M 3.5G 0% /overlay
overlayfs:/overlay 3.7G 7.8M 3.5G 0% /
tmpfs 512.0K 0 512.0K 0% /dev
In my case, I have now 3.5GB of free space !