High Speed Data Acquisition Architectures

1. High Speed Data Acquisition Architectures

2. Some Basic Architectures • Non-Buffered (streaming) • FIFO Buffered • Multiplexed RAM • “Ping Pong” Multiplexed RAM • Dual Port RAM

3. Streaming Interface Block Diagram

4. Advantages / Disadvantages of Streaming • Advantages • Simple, low cost • If only a small sample block is required, internal DSP RAM can be used for buffering • Processing takes place in real time • Disadvantages • Limited sampling speed

5. FIFO Buffered Block Diagram

6. Advantages / Disadvantages of FIFO Buffered • Advantages • Simple • Allows initial samples to be processed while subsequent samples are collected • Moderate cost, low to moderate density • Fast: 100MHz clock rates readily available • Disadvantages • Sequential access, unneeded samples must be unloaded • Calculations cannot be done “in place”

7. Multiplexed RAM Block Diagram

8. Advantages / Disadvantages of Multiplexed RAM • Advantages • Low cost • High density • Random access • Calculations can be done in place • Disadvantages • More complex than FIFO, requires multiplexers, counters, etc • RAM only available after all data has been collected. Processing of first samples cannot proceed in parallel with subsequent data collection • RAM access time may require that ADC data be demultiplexed into multiple data streams

9. “Ping Pong” Multiplexed RAM Block Diagram

10. Advantages / Disadvantages of “Ping Pong” Multiplexed RAM • Advantages • High density • Random access • One data buffer is always available to DSP/Host, so next data set is collected while first data set is processed • Calculations can be done in place • Disadvantages • Complex, requires dual RAM banks, several multiplexers, counters, etc • RAM access time may require that ADC data be demultiplexed into multiple data streams

11. Dual Port RAM Block Diagram

12. Advantages / Disadvantages of Dual Port RAM • Advantages • Simple • Random access • First data point is available for processing immediately • Calculations can be done in place • Disadvantages • Low density, high cost • RAM access time may require that ADC data be demultiplexed into multiple data streams

13. Interfaces • USB 2.0 • 10/100 LAN • Gigabit LAN • Parallel Bus (PXI, CPCI, VME, VXI, etc)

14. USB 2.0 • Advantages • Simple hardware • 480 Mbps • Widely available on desktops and laptops • Disadvantages • Can require substantial software overhead • Sharing bus with over devices limits bandwidth • Must be in close proximity to computer

15. 10/100 LAN • Advantages • Widely available on desktops and laptops • Operates over long distances • Disadvantages • Typically requires coprocessor • Can require substantial software overhead • Sharing bus with other devices limits bandwidth

16. Gigabit LAN • Advantages • 1000 Mbps • Operates over long distances • Disadvantages • Typically requires embedded SBC with operating system support • Can require substantial software overhead • Sharing bus with other devices limits bandwidth

17. Parallel Bus • Advantages • Fastest possible data transfer • DSP may not be required for some applications • Can use off the shelf SBC as controller/host processor • Host processor/OS could support other interfaces (e.g. Gigabit LAN) • Disadvantages • Expensive (requires SBC) • Size, power consumption

18. ADC14100-USB Block Diagram

19. ADC14100-USB Front Panel

20. ADC14100-USB Rear Panel

21. ADC14100-USB Features • 14 Bit 100 MSPS ADC • Analog Devices ADSP-21262 DSP • 256K x 18, 100 MHz FIFO memory • USB 2.0 Interface • RS232 Interface • Hardware decimator for lower sample rates at full analog bandwidth • 3 software selectable clock sources: • Internal 100 MHz oscillator • Internal 80 MHz oscillator • External clock