Development of a High-Speed Multi-Channel Analog Data Acquisitioning Architecture

1. Development of a High-Speed Multi-Channel Analog Data Acquisitioning Architecture L. Björk, S. Persyn, B. Walls, M. Epperly Southwest Research Institute September 2005

2. Introduction As the measurement techniques in the space science community rapidly evolve, the demand for multi-channeled, high-speed, radiation tolerant data acquisitioning systems get increasingly higher. The high volume and resolution of data, and the complexity of the in-situ processing and analysis requirements have triggered the need for faster, smaller, and easily reconfigurable DSP designs. Historically, these types of systems have been burdened with the use of multi-channels through multiplexers and the use of slow analog to digital converters. Because of that, these older systems have been forced to perform all the required processing in the initial analog stage and later in a CPU calculation, reducing reconfigurability and adding overhead. Björk 2 MAPLD 2005

3. New Demands - Highlights • Multiple detector input channels • High-speed data acquisition and conversion • High radiation tolerance • Smaller systems • Easily reconfigurable/ high versatility • Higher resolution • Greater volume of data • Increased complexity of in-situ processing Björk 3 MAPLD 2005

4. SwRI’s Response In response, Southwest Research Institute, SwRI, has developed a high-speed, multi-channel, versatile data acquisitioning architecture. This new architecture can perform reconfigurable DSP algorithms and subsequent data processing on instrument analog input signals. The overall architecture and topology was developed as part of a SwRI science instrumentation trade study and then implemented on the NASA Gamma-ray Large Area Space Telescope (GLAST) Data Processing Unit (DPU) and can easily be reconfigured for other space missions and instrument applications. Björk 4 MAPLD 2005

5. Typical Applications Typical applications: • High-Energy Particle Detectors • Video Input • Sound Input In general, any type of instrument whose output is an analog waveform where the science is related to the characteristic of the analog waveform, such as: • Pulse Height • Rise Time • Area (Integration) of the pulse Björk 5 MAPLD 2005

6. Heritage Sample and Hold Shortcomings • Data from multi-channel systems went through multiplexers before being converted in an ADC. • Radiation tolerant, high-speed ADCs were not readily available. • Processing had to be done in analog stage or in CPU, slowing the system down. • Could not process real-time, raw data. • Led to non-reconfigurable, slow systems. Björk 6 MAPLD 2005

7. High-Speed Multi-Channel Architectural Solution Björk 7 MAPLD 2005

8. Analog Input Flow • Accepts single ended or differential input. • Signal conditioning circuitry • Amplification • Attenuation • Filtering (low pass, band pass) • Clipping diodes for input voltage protection • Analog to Digital Conversion • 14-bit flash-based, pipelined • One ADC per channel Björk 8 MAPLD 2005

9. Digital Signal Processing FPGA • Easily reconfigurable state-machine • Examples of algorithms • Pulse height detection (Radiation detectors i.e. sodium iodide, NaI, or bismuth germanate, BGO) • Discrete Fourier Transform calculations, DFT (Wave analysis) • Area integration (High-energy particle detection with Solid State Detectors, SSD) • Ramp detection/calculations (Langmuir probes) • Time delay measurements (Mass spectrometry) • Algorithms developed in VHDL or Verilog Björk 9 MAPLD 2005

10. Pulse Height Detection Example Björk 10 MAPLD 2005

11. Event Controller FPGA • Drives data through compression hardware. • Lossy compression - LUT compression, i.e. 12 bit to 8 bit • Lossless compression - Rice compression • Supplies data to CPU for processing. • Software compression • Algorithms • Drives data to transmission interfaces. • LVDS/MLVDS • RS-422/RS-485 • MIL-STD-1553B • SpaceWire • Controls mission elapsed timer or vehicle time code Björk 11 MAPLD 2005

12. Example of Datatypes • Data can be processed in a compressed or non-compressed format • Raw data • Time-tagged events • Timer controlled accumulated data • Max value detection • Min value detection • Total counts Björk 12 MAPLD 2005

13. Diagram of a Full System Björk 13 MAPLD 2005

14. Example of a Full System Data Processing Unit (DPU) for the NASA Gamma-Ray Large Area Space Telescope (GLAST). • 14 detector inputs • 1 ADC per channel • DSP FPGA • EC LUT compression • 4 timer based data types • 1 time tagged data type • Some raw data sent directly to processor for processing and transmitted via serial data stream • SPARC TSC 32 bit RISC processor 20MIPS 5MFLOPS • 1553 bus, RS-422, LVDS (source packets) Björk 14 MAPLD 2005

15. Example of a Small System • MOPS is an example of a miniaturized implementation of the SwRI DSP architecture. MOPS clearly demonstrates the versatility this architecture can deliver in size as well as implementation. • A typical small system could consist of a scaled down version of a full system’s sub-sections, or only selected parts of it. For example, it may have fewer channels and/or ADCs. All processing may be done in the DSP FPGA and it may or may not be redundant or utilize compression. The data storage and interfaces may differ drastically. Miniaturized Optimized Processor for Space (MOPS) Björk 15 MAPLD 2005

16. Conclusion The SwRI developed, reconfigurable DSP architecture for space applications has many advantages compared to the traditional approach of designing a DSP system. This architecture is more efficient, faster, more compact, requires fewer resources and support circuitry, and provides a considerably reduced design cycle. The reconfigurable DSP FPGA algorithm is the core of the architecture. By processing most or all accumulated data in the FPGA, the CPU can be used for other tasks. This used to be one of the limiting factors on previous systems. Also, since very little mission specific data is processed in the analog front end, the design does not have to be altered much, if at all, between different implementations. There is a multitude of options available for data processing, compression and storage, and physical interfaces. So far, no implementation has proven to be too small or too big for this architecture. Heritage designs lead to proven, safer systems, limiting risk and increasing chance of mission success. Björk 16 MAPLD 2005