Bit Microcontroller

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HD64F3694FPV RENESAS 16 BIT FLASH 20MHz MICROCONTROLLER Microcontroller ROHS
HD64F3694FPV RENESAS 16 BIT FLASH 20MHz MICROCONTROLLER Microcontroller ROHS
$5.95
quality
HD64F3694FPV RENESAS 16 BIT FLASH 20MHz MICROCONTROLLER ROHS 5 PCS
HD64F3694FPV RENESAS 16 BIT FLASH 20MHz MICROCONTROLLER ROHS 5 PCS
$15.95
quality
HD64F3694FPV RENESAS 16 BIT FLASH 20MHz MICROCONTROLLER ROHS 55 PCS
HD64F3694FPV RENESAS 16 BIT FLASH 20MHz MICROCONTROLLER ROHS 55 PCS
$124.95
quality
HD6305Y0F HITACHI 8 BIT MROM 1MHz MICROCONTROLLER PQFP64
HD6305Y0F HITACHI 8 BIT MROM 1MHz MICROCONTROLLER PQFP64
$8.95
quality
Zilog Z86C9116FSC 8 BIT 16MHz MICROCONTROLLER PQFP44
Zilog Z86C9116FSC 8 BIT 16MHz MICROCONTROLLER PQFP44
$6.95
quality
COPEG888 DJS V 8 Bit Microcontroller with UART PLCC 44
COPEG888 DJS V 8 Bit Microcontroller with UART PLCC 44
$3.99
quality
5 NEW ZiLOG Z0868108PSC 8Mhz Microcontroller PDIP40 PCU 8bit Obsolete
5 NEW ZiLOG Z0868108PSC 8Mhz Microcontroller PDIP40 PCU 8bit Obsolete
$31.00
quality
PIC16C54 XT P 8 Bit CMOS Microcontroller in an 18 Pin Dip Package
PIC16C54 XT P 8 Bit CMOS Microcontroller in an 18 Pin Dip Package
$2.00
quality
MC68705R3L MOTOROLA 8 Bit EPROM Microcontroller EPROM GOLD
MC68705R3L MOTOROLA 8 Bit EPROM Microcontroller EPROM GOLD
$9.00
quality
Microcontroller MC9S08SE4CWL IC 8 Bit 20MHz 4KB FLASH 28 SOIC W Lot 102 pcs
Microcontroller MC9S08SE4CWL IC 8 Bit 20MHz 4KB FLASH 28 SOIC W Lot 102 pcs
$229.00
quality
5PC MICROCHIP PIC18F26K20 I ML IC FLASH MICROCONTROLLER 8BIT 64K QFN 28
5PC MICROCHIP PIC18F26K20 I ML IC FLASH MICROCONTROLLER 8BIT 64K QFN 28
$5.99
quality
8 Microchip PIC16C781 1 SS 8 Bit CMOS Microcontroller ICs
8 Microchip PIC16C781 1 SS 8 Bit CMOS Microcontroller ICs
$19.99
quality
Microchip Pic16F887 E P Microcontroller Mcu 8 Bit Pic16 20Mhz Dip 40 US Stock
Microchip Pic16F887 E P Microcontroller Mcu 8 Bit Pic16 20Mhz Dip 40 US Stock
$3.99
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R8751H INTEL 8751 Gold LCC EPROM MCS 51 8 bit Microcontroller UOS LAST ONE
R8751H INTEL 8751 Gold LCC EPROM MCS 51 8 bit Microcontroller UOS LAST ONE
$19.95
quality
INTEL P8031AH MICROCONTROLLER8 BIT CPU MOS 40 PIN PLASTIC DIP PULLED ITEM QTY 1
INTEL P8031AH MICROCONTROLLER8 BIT CPU MOS 40 PIN PLASTIC DIP PULLED ITEM QTY 1
$18.84
quality
Atmel Atmega32U4 Au Microcontroller Mcu 8 Bit Megaavr 16Mhz Tqfp 44
Atmel Atmega32U4 Au Microcontroller Mcu 8 Bit Megaavr 16Mhz Tqfp 44
$22.91
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Microchip Pic10Lf320T I Ot 8 Bit Microcontroller Pack Of 10
Microchip Pic10Lf320T I Ot 8 Bit Microcontroller Pack Of 10
$24.55
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Atmel Atxmega256A3U Au 8 Bit MicrocontrollerLow Power High Performance
Atmel Atxmega256A3U Au 8 Bit MicrocontrollerLow Power High Performance
$23.50
quality
Atmel At89C51Rc2 Slsum 8 Bit Microcontroller High Performance Flash
Atmel At89C51Rc2 Slsum 8 Bit Microcontroller High Performance Flash
$26.99
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Atmel Atxmega128A1U Au 8 Bit Microcontroller 100 Pins Tqfp Pack Of 2
Atmel Atxmega128A1U Au 8 Bit Microcontroller 100 Pins Tqfp Pack Of 2
$33.91
quality
Atmel Atxmega64A3U Au 8 Bit Microcontroller 64 Pins Tqfp Pack Of 2
Atmel Atxmega64A3U Au 8 Bit Microcontroller 64 Pins Tqfp Pack Of 2
$25.43
quality
Atmel Atxmega192A3U Au 8 Bit MicrocontrollerLow Power High Performance
Atmel Atxmega192A3U Au 8 Bit MicrocontrollerLow Power High Performance
$22.76
quality
Atmel Atxmega16A4U Au 8 Bit Microcontroller Pack Of 4
Atmel Atxmega16A4U Au 8 Bit Microcontroller Pack Of 4
$33.20
quality
Atmel Attiny84A Ssu 8 Bit Microcontroller Avr Tiny Pack Of 10
Atmel Attiny84A Ssu 8 Bit Microcontroller Avr Tiny Pack Of 10
$28.12
quality
Atmel Attiny861V 10Mu 8 Bit Microcontroller Pack Of 4
Atmel Attiny861V 10Mu 8 Bit Microcontroller Pack Of 4
$23.91
quality
Atmel Atsam4Ls2Aa Mu 32 Bit Microcontroller Sam4L Series Arm Cortex M4
Atmel Atsam4Ls2Aa Mu 32 Bit Microcontroller Sam4L Series Arm Cortex M4
$22.36
quality
1PCS W78C32BP 24 PLCC 448 Bit Microcontroller Ships from the USA
1PCS W78C32BP 24 PLCC 448 Bit Microcontroller Ships from the USA
$7.95
quality
1Pcs MC68331CFC20 MOTOROLA 32 BIT 132 PIN MICROCONTROLLER
1Pcs MC68331CFC20 MOTOROLA 32 BIT 132 PIN MICROCONTROLLER
$40.00
quality
New England Micro Solutions PIC Microcontroller 8 bit I O Board 7 25v
New England Micro Solutions PIC Microcontroller 8 bit I O Board 7 25v
$59.99
quality
Major Brands 80C31 8 Bit 32 I O 24 MHz DIP 40 Microcontroller 2 pcs
Major Brands 80C31 8 Bit 32 I O 24 MHz DIP 40 Microcontroller 2 pcs
$6.50
quality
ST Micro ST7FLCD1G9M1 IC 8 Bit Microcontroller MCU ST7 Core Lot of 5 Pcs NEW
ST Micro ST7FLCD1G9M1 IC 8 Bit Microcontroller MCU ST7 Core Lot of 5 Pcs NEW
$9.95
quality
1 PC DS2244T 2AT DALLAS SEMI 8 BIT 24MHz MICROCONTROLLER 30 PIN SIMM
1 PC DS2244T 2AT DALLAS SEMI 8 BIT 24MHz MICROCONTROLLER 30 PIN SIMM
$12.95
quality
Qty 1 Microchip PIC18F8723 I PT 128KB 8 bit microcontroller US Seller
Qty 1 Microchip PIC18F8723 I PT 128KB 8 bit microcontroller US Seller
$10.19
quality
1 PC W77C32 40 WINBOND 8 BIT 40MHz MICROCONTROLLER PDIP40
1 PC W77C32 40 WINBOND 8 BIT 40MHz MICROCONTROLLER PDIP40
$7.95
quality
AMD P8031AH Single Chip 8 Bit Microcontroller Microcomputer CPU
AMD P8031AH Single Chip 8 Bit Microcontroller Microcomputer CPU
$4.00
quality
Intel P8344AH 8 Bit Microcontroller Microcomputer CPU
Intel P8344AH 8 Bit Microcontroller Microcomputer CPU
$10.00
quality
Intel P8039AHL 8 Bit Microcontroller Microcomputer CPU
Intel P8039AHL 8 Bit Microcontroller Microcomputer CPU
$4.00
quality
P89C664HBBD Microcontroller IC 8 Bit 33MHz 64KB 64K x 8 FLASH 44 LQFP LOT 13
P89C664HBBD Microcontroller IC 8 Bit 33MHz 64KB 64K x 8 FLASH 44 LQFP LOT 13
$28.00
quality
25 TMP68HC11A0T TOSHIBA  MC68HC11A0FN MICROCONTROLLER 68HC11 8 BIT 52 PIN PLCC
25 TMP68HC11A0T TOSHIBA MC68HC11A0FN MICROCONTROLLER 68HC11 8 BIT 52 PIN PLCC
$74.99
quality
Microchip PIC16LC84 04I SO 8 bit CMOS EEPROM Microcontroller Lot of 5 pcs
Microchip PIC16LC84 04I SO 8 bit CMOS EEPROM Microcontroller Lot of 5 pcs
$17.99
quality
TP8798 INTEL 16 BIT 12 MHz EPROM HMOS Microcontroller 48PIN P DIP New 1 piece
TP8798 INTEL 16 BIT 12 MHz EPROM HMOS Microcontroller 48PIN P DIP New 1 piece
$5.95
quality
1 X MC68HC11K1CFN4 PULLS MICROCONTROLLER MCU 8 BIT HC11 4MHZ PLCC 84 IN1A
1 X MC68HC11K1CFN4 PULLS MICROCONTROLLER MCU 8 BIT HC11 4MHZ PLCC 84 IN1A
$4.99
quality
XC68HC705B32CFN microcontroller 8 bit 52 pin
XC68HC705B32CFN microcontroller 8 bit 52 pin
$9.99
quality
Microchip Pic16F818 I P Microcontroller Mcu8 BitPic1620MhzDip 18 get it fast
Microchip Pic16F818 I P Microcontroller Mcu8 BitPic1620MhzDip 18 get it fast
$2.99
quality
1 PC MC68340PV16E FREESCALE 32 BIT 1678MHz MICROCONTROLLER PQFP144
1 PC MC68340PV16E FREESCALE 32 BIT 1678MHz MICROCONTROLLER PQFP144
$19.95
quality
QTY 5 PIC16C77 20 P MICROCHIP 40 PIN DIP 8 bit MICROCONTROLLER NOS
QTY 5 PIC16C77 20 P MICROCHIP 40 PIN DIP 8 bit MICROCONTROLLER NOS
$24.99
quality
1 PCs INTEL P8049AH 8 Bit Microcontroller Microcomputer DIP40
1 PCs INTEL P8049AH 8 Bit Microcontroller Microcomputer DIP40
$4.99
quality
PIC16C74A JW MICROCHIP 40 PIN CERAMIC DIP W WINDOW 8 bit MICROCONTROLLER
PIC16C74A JW MICROCHIP 40 PIN CERAMIC DIP W WINDOW 8 bit MICROCONTROLLER
$7.99
quality
QTY 6 MC68HC705J1ACDW MOTOROLA SOIC 20 8 bit MICROCONTROLLER NOS
QTY 6 MC68HC705J1ACDW MOTOROLA SOIC 20 8 bit MICROCONTROLLER NOS
$19.99
quality
Freescale Semiconductor Mc9S12Xep100Mag Hcs12 16 Bit Microcontroller Ic
Freescale Semiconductor Mc9S12Xep100Mag Hcs12 16 Bit Microcontroller Ic
$46.95
quality
NEW P 80C32 12 Matra CMOS 0 to 12 MHz Single chip 8 Bit Microcontroller NOS
NEW P 80C32 12 Matra CMOS 0 to 12 MHz Single chip 8 Bit Microcontroller NOS
$5.00
quality
NEW P8749H HMOS SINGLE COMPONENT 8 BIT MICROCONTROLLER NOS
NEW P8749H HMOS SINGLE COMPONENT 8 BIT MICROCONTROLLER NOS
$5.00
quality
Microchip Pic24F16Ka304 I Pt Microcontroller Mcu 16 Bit Pic24 32Mhz Tqfp 44
Microchip Pic24F16Ka304 I Pt Microcontroller Mcu 16 Bit Pic24 32Mhz Tqfp 44
$400.00
quality
9pcs MICROCHIP MICROCONTROLLER MCU 8BIT 35KB 18SOIC PIC16C622 20 SO
9pcs MICROCHIP MICROCONTROLLER MCU 8BIT 35KB 18SOIC PIC16C622 20 SO
$14.99
quality
HD63705V0P 8 Bit Microcontroller CMOS Integrated Circuit Hitachi 1 piece
HD63705V0P 8 Bit Microcontroller CMOS Integrated Circuit Hitachi 1 piece
$20.00
quality
WINDBOND W78C32CP 24 8 BIT MICROCONTROLLER 8 BIT 24 PLCC NEW ITEM QUANTITY 5
WINDBOND W78C32CP 24 8 BIT MICROCONTROLLER 8 BIT 24 PLCC NEW ITEM QUANTITY 5
$18.84
quality
atmel attiny84a pu microcontroller mcu 8 bit attiny 20mhz dip 14 5 pieces
atmel attiny84a pu microcontroller mcu 8 bit attiny 20mhz dip 14 5 pieces
$27.13
quality
5 PCS PIC16LC84 04 SO MICROCHIP 8 BIT EEPROM 4MHz RISC MICROCONTROLLER SOIC18
5 PCS PIC16LC84 04 SO MICROCHIP 8 BIT EEPROM 4MHz RISC MICROCONTROLLER SOIC18
$15.75
quality
SCN8035A 8 Bit Microcontroller 40 Pin Dip New Old Stock
SCN8035A 8 Bit Microcontroller 40 Pin Dip New Old Stock
$4.50
quality
LOT OF 10 NEW MICROCHIP PIC16F877 20 P 8 BIT FLASH MICROCONTROLLER
LOT OF 10 NEW MICROCHIP PIC16F877 20 P 8 BIT FLASH MICROCONTROLLER
$75.00
quality
MICROCHIP PIC16F688 I P MICROCONTROLLER MCU 8 BIT PIC16 20MHZ PDIP 14 1
MICROCHIP PIC16F688 I P MICROCONTROLLER MCU 8 BIT PIC16 20MHZ PDIP 14 1
$9.76
quality
MICROCHIP PIC12F683 I P MICROCONTROLLER MCU 8 BIT PIC12 20MHZ DIP 8 1 piece
MICROCHIP PIC12F683 I P MICROCONTROLLER MCU 8 BIT PIC12 20MHZ DIP 8 1 piece
$13.44
quality
Atmel Semicondu ATMEGA328P PU Atmel ATMega328 32kB Flash Microcontroller 8bit
Atmel Semicondu ATMEGA328P PU Atmel ATMega328 32kB Flash Microcontroller 8bit
$16.53
quality
iSSI IS80C32 40PL 8 Bit Microcontroller
iSSI IS80C32 40PL 8 Bit Microcontroller
$20.00
quality
QuickLogic QL16X24B OPF100C 8 Bit CMOS Micro Controller NEW
QuickLogic QL16X24B OPF100C 8 Bit CMOS Micro Controller NEW
$15.95
quality
2 PCS SILICON LABS C8051F340 GQ IC MCU 8BIT 64KB FLASH 48TQFP MICROCONTROLLER US
2 PCS SILICON LABS C8051F340 GQ IC MCU 8BIT 64KB FLASH 48TQFP MICROCONTROLLER US
$15.00
quality
AT89C52 24JC Atmel 8 Bit Microcontroller with 8K bytes Flash 44P PLCC
AT89C52 24JC Atmel 8 Bit Microcontroller with 8K bytes Flash 44P PLCC
$7.30
quality
MOTOROLA P N MC68HC11E1VFN PLCC 52 8 BIT Microcontroller SMD
MOTOROLA P N MC68HC11E1VFN PLCC 52 8 BIT Microcontroller SMD
$7.00
quality
ADUC814BRU ANALOG DEVICES Microcontroller 8 bit 28 Pin TSSOP 1 UNIT
ADUC814BRU ANALOG DEVICES Microcontroller 8 bit 28 Pin TSSOP 1 UNIT
$12.55
quality
1 PC P80C51BH 7755 INTEL DTSP H 8 BIT MROM 12MHz MICROCONTROLLER PDIP40
1 PC P80C51BH 7755 INTEL DTSP H 8 BIT MROM 12MHz MICROCONTROLLER PDIP40
$4.95
quality
P87C554SFAA512 NXP 80C51 8 Bit Microcontroller 512Byte Ram 10 bit A D I2C PWM
P87C554SFAA512 NXP 80C51 8 Bit Microcontroller 512Byte Ram 10 bit A D I2C PWM
$20.10
quality
AMD ELANSC400 33AI BIT FLASH 33 MHz MICROCONTROLLER INDUSTRIAL NEW RARE 19
AMD ELANSC400 33AI BIT FLASH 33 MHz MICROCONTROLLER INDUSTRIAL NEW RARE 19
$15.20
quality
NOS Kenwood UPD78045AGF025 8 bit single chip MOS microcontroller
NOS Kenwood UPD78045AGF025 8 bit single chip MOS microcontroller
$25.00
quality
INTEL D8742 8 Bit MicroController 40 Pin Ceramic Dip New Lot Quantity 2
INTEL D8742 8 Bit MicroController 40 Pin Ceramic Dip New Lot Quantity 2
$9.95
quality
Microchip Pic16F916 I Ss Microcontroller Mcu 8 Bit Pic16 20Mhz Ssop 28
Microchip Pic16F916 I Ss Microcontroller Mcu 8 Bit Pic16 20Mhz Ssop 28
$21.91
quality
5X Microchip Pic18F44K20 I Pt Microcontroller Mcu 8 Bit Pic18 64Mhz
5X Microchip Pic18F44K20 I Pt Microcontroller Mcu 8 Bit Pic18 64Mhz
$34.38
quality
Microchip Pic24Fj32Ga002 I So Microcontroller Mcu 16 Bit Pic24 32Mhz Soic 28
Microchip Pic24Fj32Ga002 I So Microcontroller Mcu 16 Bit Pic24 32Mhz Soic 28
$36.48
quality
Microchip Pic18F1330 I P Microcontroller Mcu 8 Bit Pic18 40Mhz Dip 18
Microchip Pic18F1330 I P Microcontroller Mcu 8 Bit Pic18 40Mhz Dip 18
$22.07
quality
Microchip Pic18F46J11 I Pt Microcontroller Mcu 8 Bit Pic18 48Mhz Tqfp 44
Microchip Pic18F46J11 I Pt Microcontroller Mcu 8 Bit Pic18 48Mhz Tqfp 44
$22.59
quality
Microchip Pic24Fj64Ga002 I So Microcontroller Mcu 16 Bit Pic24 32Mhz Soic 28
Microchip Pic24Fj64Ga002 I So Microcontroller Mcu 16 Bit Pic24 32Mhz Soic 28
$39.89
quality
Microchip Pic18F45K22 E Pt Microcontroller Mcu 8 Bit Pic18 64Mhz Tqfp 44
Microchip Pic18F45K22 E Pt Microcontroller Mcu 8 Bit Pic18 64Mhz Tqfp 44
$22.14
quality
74K8567 Microchip Pic16F884 I P Microcontroller Mcu 8 Bit Pic16 20Mhz Dip 40
74K8567 Microchip Pic16F884 I P Microcontroller Mcu 8 Bit Pic16 20Mhz Dip 40
$19.17
quality
5X Microchip Pic16F887 E P Microcontroller Mcu 8 Bit Pic16 20Mhz Dip 40
5X Microchip Pic16F887 E P Microcontroller Mcu 8 Bit Pic16 20Mhz Dip 40
$36.25
quality
Microchip Pic18F2420 I So Microcontroller Mcu 8 Bit Pic18 40Mhz Soic 28
Microchip Pic18F2420 I So Microcontroller Mcu 8 Bit Pic18 40Mhz Soic 28
$22.61
quality
Microchip Pic18F46K22 I Pt Microcontroller Mcu 8 Bit Pic18 64Mhz Tqfp 44
Microchip Pic18F46K22 I Pt Microcontroller Mcu 8 Bit Pic18 64Mhz Tqfp 44
$22.29
quality
5x Microchip Pic18F45K22 I Pt Microcontroller Mcu 8 Bit Pic18 64Mhz
5x Microchip Pic18F45K22 I Pt Microcontroller Mcu 8 Bit Pic18 64Mhz
$37.16
quality
5X Microchip Pic18F26J11 I Sp Microcontroller Mcu 8 Bit Pic18 48Mhz Dip 28
5X Microchip Pic18F26J11 I Sp Microcontroller Mcu 8 Bit Pic18 48Mhz Dip 28
$40.00
quality
Microchip Pic18F2420 I Sp Microcontroller Mcu 8 Bit Pic18 40Mhz Ndip 28
Microchip Pic18F2420 I Sp Microcontroller Mcu 8 Bit Pic18 40Mhz Ndip 28
$22.79
quality
Microchip Pic18F26J50 I So Microcontroller Mcu 8 Bit Pic18 48Mhz Soic 28
Microchip Pic18F26J50 I So Microcontroller Mcu 8 Bit Pic18 48Mhz Soic 28
$22.07
quality
Microchip Pic16F870 I Sp Microcontroller Mcu 8 Bit Pic16 20Mhz Ndip 28
Microchip Pic16F870 I Sp Microcontroller Mcu 8 Bit Pic16 20Mhz Ndip 28
$22.26
quality
5X Microchip Pic18Lf24K22 I Ml Microcontroller Mcu 8 Bit Pic18 64Mhz Qfn 28
5X Microchip Pic18Lf24K22 I Ml Microcontroller Mcu 8 Bit Pic18 64Mhz Qfn 28
$34.77
quality
Microchip Pic16C57 Hs So Microcontroller Mcu 8 Bit Pic16 20Mhz Soic 28
Microchip Pic16C57 Hs So Microcontroller Mcu 8 Bit Pic16 20Mhz Soic 28
$25.50
quality
Microchip Pic24Hj32Gp202 I Sp Microcontroller Mcu 16 Bit Pic24 80Mhz Dip 28
Microchip Pic24Hj32Gp202 I Sp Microcontroller Mcu 16 Bit Pic24 80Mhz Dip 28
$22.87
quality
Microchip Pic16F876 20 So Microcontroller Mcu 8 Bit Pic16 20Mhz Soic 28
Microchip Pic16F876 20 So Microcontroller Mcu 8 Bit Pic16 20Mhz Soic 28
$25.61
quality
5X Microchip Pic24F16Km202 I So Microcontroller Mcu 16 Bit Pic24 32Mhz
5X Microchip Pic24F16Km202 I So Microcontroller Mcu 16 Bit Pic24 32Mhz
$37.16
quality
Microchip Pic18F2220 I Sp Microcontroller Mcu 8 Bit Pic18 40Mhz Ndip 28
Microchip Pic18F2220 I Sp Microcontroller Mcu 8 Bit Pic18 40Mhz Ndip 28
$24.21
quality
Microchip Pic18F86J60 I Pt Microcontroller Mcu 8 Bit Pic18 40Mhz Tqfp 80
Microchip Pic18F86J60 I Pt Microcontroller Mcu 8 Bit Pic18 40Mhz Tqfp 80
$23.45
quality
Microchip Pic18Lf2220 I So Microcontroller Mcu 8 Bit Pic18 40Mhz Soic 28
Microchip Pic18Lf2220 I So Microcontroller Mcu 8 Bit Pic18 40Mhz Soic 28
$24.47
quality
Microchip Pic24Ep512Gp806 I Pt Microcontroller Mcu16 BitPic24140MhzTqfp 64
Microchip Pic24Ep512Gp806 I Pt Microcontroller Mcu16 BitPic24140MhzTqfp 64
$27.84
quality
5X Microchip Pic18F14K50 I P Microcontroller Mcu 8 Bit Pic18 48Mhz
5X Microchip Pic18F14K50 I P Microcontroller Mcu 8 Bit Pic18 48Mhz
$35.91
quality
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Bit Microcontroller

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Precision32 32-bit Microcontroller Overview

High-Performance Data Acquisition on USB

A common belief among engineers is that, to get the best performance, a PC based data acquisition module must plug into the PCI bus. Properly implemented, however, a data acquisition module can use the PC's USB 2.0 port to pump data into a PC as fast as PCI-based cards. The keys to achieving this performance are a hardware USB interface on the module and optimized driver software for the host system.

Because the Universal Serial Bus (USB) was originally developed to replace lowspeed peripheral cabling, many engineers fail to see its potential as a high performance data acquisition channel. The original USB specification did offer only a modest bit rate, but USB 2.0 handles 480 Mbits/sec, fast enough to handle 60 Mbyte/sec data streams. Even with the protocol reserving some bandwidth for interrupts and control transfers, and the header overhead on data packets, the bus can easily sustain more than 10 Mbytes/sec of continual data transfer. This is fast enough to support extremely high performance data acquisition (DAQ) hardware.

Utilizing the USB as a data portal provides many advantages for data acquisition (DAQ). For one, the external connector and "plug-and-play" software installation of USB peripherals means that users do not have to open their PC, then set-up and configure the hardware in order to begin acquiring data. The USB-based DAQ module sets itself up upon installation. Addressing and other potential resource utilization conflicts resolve automatically.

Software for handling the data also becomes simpler to implement. The host system USB drivers separate data streams into logical channels called "pipes." This means that the host system software will automatically form a logical connection from a DAQ channel to a destination within the application software, simplifying software and hardware set-up. Applications simply need to identify the logical pipe they wish to connect with and the system software ensures that data travels to the right destination. Application software does not need to know the details of peripheral addressing, interrupt placement, or other installation dependent parameters as it must for PCI plug-in cards. The USB also has electronic advantages. The bus can power the peripheral (within limits) so that the DAQ system does not need its own power source. This further eases system installation and use and has the added benefit of removing the sensitive A/D converters and amplifiers from the electrically noisy environment inside the PC's housing. Unlike PCI plug-in cards, a USB-based DAQ module is easily shielded for achieving high bit-level resolution. The benefits of USB operation are compelling for a DAQ system, but implementing the system does require care in order to ensure a high-bandwidth connection. Engineers often assume that high data-rate systems should use the USB data transfer mode with the highest raw bandwidth and least overhead penalty: isochronous transfer. But isochronous transfers are a "best-effort" channel. Data that suffers from errors cannot be resent. The proper mode to use for DAQ on USB is the bulk transfer mode.

1). This mode supports the resending of corrupted packets, ensuring data accuracy, and allows fairly large 512-byte blocks, keeping overhead effects down.

The drawback is that bulk transfers do not have guaranteed timing. The USB host controller assigns bandwidth for bulk transfers but reserves priority for interrupt and control transfers. Thus, the bandwidth obtained by using bulk transfers is an average - not a sustained - data rate while the DAQ module needs to send data at a constant speed.

There are two approaches to dealing with the uncertainty in the instantaneous bandwidth available for bulk transfers. One is to keep the data rate low in order to maximize the likelihood that bandwidth available will always exceed the DAQ module's data rate. This is the simpler approach, but results in severe underutilization of USB's potential.

The alternative approach is for the DAQ module to incorporate FIFO buffering to hold data while waiting for the bus to become available. Dual buffers are needed in the module - one to fill while the other is emptying. The larger the buffers, the more tolerant the module becomes of shifting bandwidth availability and the closer its data rate can approach the average bandwidth available.

In addition to the FIFO buffering on the DAQ module, the software drivers should allocate buffer space in the host system at the receiving end. This decouples the host system's data processing activity from the data acquisition so that neither activity can delay or impede the other's performance.

While FIFO buffering maximizes the DAQ module's ability to utilize the available bulk transfer bandwidth, however, it is not the only way to improve the achievable speed on the USB. The module's USB interface hardware and latency in the host controller software can seriously constrain achievable USB data rates if not implemented with high performance in mind. For the interface hardware, using a state-machine hardware controller optimized for 512-byte transfers (the largest bulk transfer packet) produces a much faster interface than the use of a software-dependent USB microcontroller.

On the host side, careful driver design can reduce latency by speeding the host system's response to incoming USB data. The traditional Windows drivers allocate buffer space in response to an incoming USB transfer, taking many milliseconds getting ready to receive data once the DAQ module declares data ready to send. Drivers that are proactive instead of reactive, pre-allocating buffer spaces of the right size can decrease host latency by an order of magnitude. These are not simply theoretical suggestions. Data Translation has achieved a data rate of 250k samples/sec on 12 simultaneous channels with its DT9836 USB data acquisition module and 2M samples/sec on 2 simultaneous channels at with the DT9832A. Experience has shown that the USB can provide reliable, sustainable data rates as great as 10.9 Mbytes/sec, corresponding to sample rates of 5.45M samples/sec. The potential exists to take USB-based data acquisition to even higher levels with additional buffering and driver optimization.

But a high data rate is not all that is required of a high-performance DAQ module. Issues such as accuracy, aperture uncertainty, and noise levels are equally important. Further, the inclusion of additional capabilities such as digital I/O lines, counter/timers, analog outputs, and quadrature encoders can greatly increase the utility of a DAQ module. The DT9832 and DT9836 series offer all of these features.

Accuracy in a high-performance DAQ module has many facets. The most obvious is the A/D converter's resolution. The Simultaneous Series offer 16-bit A/D conversion: 2 channels at 2.0 MHz for the DT9832A, 4 channels at 1.25 MHz for the DT9832, and 6 or 12 channels at 225 kHz for the DT9836. The modules are fabricated with 12-layer boards, keeping the signal integrity intact and typically achieving an ENOB (effective number of bits) rating of greater then 14-bits.

Accuracy also involves timing, however, especially in a multi-channel DAQ module. In order to properly compare and correlate sampled signals it is important to know the relative timing of samples from one channel to the next. Most DAQ systems use a single A/D converter with a multiplexer front-end to handle multiple channels. This results in each channel's signal being sampled at a different time, forcing the use of interpolation to bring the signal data into temporal alignment and resulting in relative timing errors or phase noise. Ideally, the samples for all channels should be made simultaneously to eliminate phase noise.

The DT9836 and DT9832 series modules do not use a multiplexer. Each channel has its own track-and-hold stage with an independent successive-approximation A/D converter (see Figure 4). The converters use a common clock and the track-and-hold stages have a common trigger, so that the modules offer true simultaneous sampling. The channels have an aperture delay of 35 nsec with uncertainty (aperture jitter) of 1 nsec, and channels are well matched so that there is less than 5 nsec difference between channels. This virtually eliminates phase noise in data.

With sample rate, bit accuracy, and timing accuracy at high levels, the availability of additional features is simply a performance bonus. The Simultaneous Series offer these extras, as shown in Figure 2. Each module includes two 16-bit D/A channels, 16 digital output channels, 16 digital input channels, two 32-bit counter timers, and 3 quadrature encoders. The additional digital I/O lines provide considerable flexibility for incorporating functions such as time stamping, pattern recognition, and synchronization with external events. The counter/timers offer a convenient means of triggering test events while the quadrature decoders simplify the use of the module with X/Y positioning and rotation.

Supporting these additional signal lines means that the data channel must be fast enough to handle the additional signal and control bits without impacting the module's sampling rate. The USB is fast enough. It has proven that it can provide the needed capacity, and offers significant ease-of-use benefits. There is no longer a need to pry open a PC to assemble a high-performance DAQ system. Simply plug one in to the USB port.

For related images and graphs, see: http://www.datx.com/white_papers/High-Performance-DAQ-on-USB-white-paper.pdfTim Ludy is a Product Marketing Manager with Data Translation. Mr. Ludy graduated from Northeastern University with a degree in Computer Science.
http://www.datx.comemail: tludy@datx.com

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