Infineon goes Cortex-M4 for embedded networks
An embedded networking demonstrator with Infineon’s Cortex-M4 based XMC4000 microcontroller has been designed to show how low-cost hardware with a modest memory and no operating system, can support network functions via different physical interfaces.
With its microcontrollers, Infineon has for many years focused on its own processor cores. However, with its latest XMC4000 microcontroller family, it has for the first time decided to use an ARM processor core, the Cortex-M4.
Peripheral modules include the CCU4 and CCU8 timer modules, with the aid of which complex PWM patterns can be created for motor control, power conversion and general purpose applications.
The addition of Ethernet and USB interfaces means the devices can be used in applications in where Infineon’s microcontrollers were seldom ever before used.
For evaluating the advantages and drawbacks of different embedded networking options, Arrow has developed the iXperience M4 embedded networking demonstrator based on an XMC4500 microcontroller.
Along with Ethernet and USB, it includes a WLAN module.
All available network functionalities, from TCP/IP Stack and DHCP client through auto-IP and ZeroConf to TFTP and web server, can be provided via Ethernet, WLAN and – using the CDC/ECM profile – via USB.
A number of these network interfaces can also be employed at the same time and even switched between by software switch.
Auto-IP and DHCP mean that IP configuration is unnecessary in almost every network environment. Instant messaging enables remote access even without port forwarding or the use of a public IP address.
The networking software from Sevenstax is supplemented by the embedded USB protocol stack from Thesycon, which implements the CDC/ECM profile as the third network interface in the demonstrator.
Although USB is, by definition, only intended for point-to-point connections between a host and a device, and thus appears to be rather unsuitable for use as a network medium, there are a number of arguments for making an exception in certain cases: Micro-USB ports are more compact and far better suited to flat portable devices than RJ45 ports, moreover, alongside data, they also transfer power to be supplied to the connected device.
USB PHYs are already normally integrated into USB-capable microcontrollers and are satisfied with low power consumption.
Galvanic insulation with the aid of additional components such as signal transformers or optocouplers is not required by the USB specification. As a result, there are benefits in terms of component costs and size.
The success of WLAN (IEEE802.11) in PCs and consumer products has resulted in the easy availability of a WLAN adapter in a USB stick for just a few euros.
It is tempting to use precisely this WLAN stick in the embedded area too. However, this is almost inconceivable in almost all devices. Drivers are only available for Windows and Linux and frequently not in the source code.
A USB host interface with the necessary software support is not present in every embedded processor system. Furthermore, USB sticks generally only support the commercial temperature range of 0 to 70 °C and respond sensitively to tough ambient conditions. The resulting software expense alone only makes sense if very large numbers are needed.
If the numbers are manageable, the use of an embedded WLAN module is normally to be recommended. Due to lower development and maintenance costs.
Many of these modules also include the whole WLAN stack and a simple TCP/IP stack in the module firmware. By means of UART or SPI, they can also be connected to a simple microcontroller, since only a relatively small and easily transportable driver is needed, which the module producer makes available in the source code and for different microcontroller platforms.
Such embedded WLAN modules are also called self-contained modules. As soon as an embedded Windows or embedded Linux operating system is used on the host processor, embedded WLAN modules with an SDIO interface make sense.
These modules are closely related to the abovementioned USB sticks in terms of functionality, since they also require a comprehensive host driver, which, however, is provided by the module or chip producers. For embedded processors without an SDIO interface, operation is also often possible via an SPI port.
Depending on bandwidth requirements and the space needed, in the different module families there exist derivatives with and without an antenna or U.FL port as well as with support for IEEE802.11a (5 GHz band) and IEEE802.11n (fast WLAN with 150 Mbit/s).
In some cases, the TCP/IP stack of self-contained modules can also be avoided, allowing a more comprehensive and higher-performing TCP/IP stack to be used on the host microcontroller.
Steve Clark is marketing and engineering director, Arrow Electronics UK