Electronic Design
Fixed-Point DSP Delivers For Less Than $2

Fixed-Point DSP Delivers For Less Than $2

Low power and low pricing are major features of Texas Instruments' (TI) fixed-point 16- bit DSP. Pricing that starts at $1.95. The chips are software-compatible with other C55x devices. This includes support for TI's DSP/BIOS kernel. A FFT hardware accelerator is available in the high end TMS320C5535.

It comes in 50 MHz and 100 MHz versions that can execute one or two instructions per cycle. The DSP core has dual ALUs and dual multipliers (Fig. 1). The former has a total active power under 0.15 mW/MHz (at 1.05V) and under 0.22 mW/MHz at 100 MHz (at 1.3V).

The TMS320C553x family can handle a range of applications including advanced audio processing. To highlight this application area, TI is has put together the $99 C5535 eZdsp development kit (Fig. 2). I had a chance to check one out and it is really slick.

  TMS320 C5532 TMS320 C5533 TMS320 C5534 TMS320 C5535
CPU single 16-bit fixed point C55x core
Peak MMACS 100,200
Frequency
50 MHz,100 MHz
Power Total active power under 0.15 mW/MHz at 50 MHz & 1.05V; under 0.22 mW/MHz at 100 MHz & 1.3V
RAM
64 KB 128 KB 256 KB 320 KB
ROM
128 KB 128 KB 128 KB 128 KB
DM
4 4-channel DMA
USB  none 1 1 1
MMC/SD 2
ADC  none  none  none 4-channel 10-bit
On-Chip Regulators 1 2 3 3
LCD Bridge  none  none  none 1
I2C 1
I2S 4
UART (SCI) 1
SPI 1
Timers 3 32-bit GP,1 WD,1 RTC
Boot Loader Available Yes
Hardware Accelerators  none  none  none FFT
Core Supply 1.3 V,1.05 V
IO Supply 1.8 V,2.5 V,2.8 V,3.3 V
Operating Temperature -10C to 70C,-40C to 85C
Package 12 mm by 12 mm BGA package with 0.8 mm pitch



The C5535 eZdsp development board (Fig. 3) has USB support that can be used a digital audio interface as well as a USB port for the XDS100 JTAG debugging tools. Support includes TI’s software framework for USB audio class and human interface device (HID). The board and software implement a USB media player. The boot software is stored on an 8 Mbyte serial flash and there is a 2 Gbyte microSD card as well. An SD card adapter, USB cable and an inexpensive microphone/headset are also included with the kit.

The audio demo software has volume control via on-board buttons and status presented on a tiny 96- by 16-pixel I2C OLED display. A very small CD has a full copy of TI's Code Composer Studio integrated development environment (IDE). It also includes source code so I was able to build on the demo.

There is a 60-pin expansion connector that provides access to most signals allowing the board to be plugged into a custom interface. Around the DSP is a pair of headers for TI's wireless modules. I have some here but didn't have a chance to program them using the DSP.

Overall, the kit and DSP are well designed and easy to program. The documentation is good and even the Gerbers for the board are available. I like the wireless support and may take advantage of it in the future.

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