HelloSoft has optimized its software-only Linux VoIP stack for a single-core ARM-based system-on-chip (SoC) from Toshiba America Electronics Corporation (TAEC). The combined hardware/software design simplifies VoIP phones, eliminating the separate DSP (digital signal processor) and associated bus… and memory systems traditionally used in VoIP phone designs.

(Click for larger view of White Eagle Systems Technology reference board for TAEC T6TC1XB-0001)

The Toshiba T6TC1XB-0001 SoC is a fairly inexpensive and humble chip released in April of 2003 as a general purpose chip for low-end networking equipment. It runs at only 150MHz. Yet, the HelloSoft VoIP stack is able to process two channels of voice on the processor, according to the companies, due to its efficient implementation of signal processing algorithms.

TAEC Director of Engineering SoC Development Bob Uvacek explains that steadily advancing RISC processing capabilities mean that complex algorithms naturally migrate toward software-only approaches. “With everything, the general trend is that it starts in hardware, then goes to DSP, then finishes with RISC. For example, five years ago, video was only hardware. Today, it is running on DSPs. In five years, it will be running on RISC. 4G cell phones — video phones with high-speed links — today, that's only done in hardware, but in five years it will be done on DSPs.”

Uvacek adds that single-core RISC designs save money, reduce design time and system complexity, and result in lower power consumption, to name a few advantages.

HelloSoft's software VoIP stack

HelloSoft first announced its software-only “Integrator” software stack for the ARM926EJ-S core in April of 2003. The stack implements all VoIP functions, including G.711, G.726, G.723.1 and G.729AB vocoders, G.168-2000 Line Echo Canceller, Voice Activity Detection (VAD), Comfort Noise Generation (CNG), Jitter Buffer, Packet Loss Concealment (PLC), DTMF Tone Detection and Generation, Call Progressive Tone (CPT), SIP/RTP/RTCP Call Signalling and Control, and multi-channel system-level framework, the company says.

The stack runs on embedded Linux on top of an ARM926EJ-S core. It supports a 2.4.21-rmk2 based embedded Linux implementation for the TAEC SoC available from Belgian embedded Linux specialist Mind, along with a development board for the chip available from White Eagle Technology (pictured above).

The Toshiba T6TC1XB-001 SoC

TAEC's T6TC1XB-001 has no special hardware acceleration features, but rather is simply a basic implementation of the ARM926EJ-S core, according to Uvacek, that Toshiba initially produced in order to show off its SoCMosaic program. SoCMosaic is a mix-and-match SoC program that lets customers integrate off-the-shelf IP (intellectual property) blocks with a standardized bus, taping out their own custom designs in as little as six months, according to TAEC.

The T6TC1XB-001 embedded controller runs at 150MHz, and features two full-duplex Ethernet 10/100 Media Access Controllers (MAC), an ARM926EJ-S core, 2 x 16KB cache, 8KB Static SRAM, MMU (memory management unit), RTC (real-time clock), counter, interrupt controller, UART (universal asynchronous receiver transmitter), watchdog timer, GPIO (general purpose input/output), 33MHz PCI (peripheral component interconnect), static and non-volatile memory (Flash/SRAM/ROM) interface controller, SDRAM controller, DMA (direct memory access), and JTAG (joint test action group) Scan/ BIST.

HelloSoft CEO Krishna Yarlagadda said, “The Toshiba T6TC1XB-001 embedded controller-based design together with HelloSoft's expertise in utilizing RISC processors efficiently for complex DSP algorithms enabled us to develop this high-performance, ultra low-cost VoIP solution.”

“The solution [reduces] the cost and complexity of developing VoIP phone systems. [It] is powerful enough to implement two channels of voice for VoIP phones, wireless IP phones, residential gateways, integrated access devices and other VoIP-enabled devices,” said Richard Tobias, VP of TAEC's ASIC and Foundry business unit.

HelloSoft competitor Trinity Convergence also offers a software-only VoIP stack for SoCs based on the ARM926EJ-S core.

Availability

Voice components and protocols are available now from HelloSoft. The Toshiba T6TC1XB-0001 embedded controller and its reference design are available now from TAEC, priced at $13.50 each in 1,000-piece quantities. A reference board for the chip is currently available from White Eagle Technology, while Mind currently offers a Linux 2.4.21-rmk2 based board support package and Linux support services for the design.

 
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