2.13 - Hardware Revision Notes

U3A = Revision 1.20
U3B = Revision 1.21
U3C = Revision 1.30

Starting September of 2006, all U3 shipments changed from hardware revision 1.20 to 1.21. Following are the some of the main changes in revision 1.21:

• The default timer clock frequency is 48 MHz.
• All TimerBaseClock frequencies are twice the previous frequencies.
• The input timer edge limit is now 30,000 edges/second, compared to the old limit of 10,000 edges/second.
• Stream mode is now supported. See Section 3.2.
• Other new functions are supported, including Watchdog, SPI, Asynch, I2C, and SHT1X.
• Typical supply current is 50 mA.

Revision 1.20 can be upgraded to 1.21 by LabJack for a small fee. For information about upgrading a rev 1.20 unit, contact LabJack Corporation.

Hardware revision 1.30 was released in mid-March 2008 with 2 variations: U3-LV and U3-HV. The U3-LV is the most compatible with the previous U3, and the only changes possibly affecting backwards compatibility are:

• Timers/Counters cannot appear on FIO0-3. TimerCounterPinOffset must be 4-8. A value of 0-3 will result in an error. This error can be suppressed by a power-up default setting in LJControlPanel. If suppressed, a 0-3 will result in an offset of 4.
• The 3.66 reference voltage is no longer available on the REF/DAC1 terminal.
• There is no longer a buzzer.
• SDA terminal is gone. SCL terminal changed to SPC.
• UART (Asynch functionality) no longer uses SDA and SPC terminals, but rather uses terminals dynamically assigned after timers and counters. Also, the BaudFactor is different.

Other changes:

• Analog outputs are now specified for 10-bit resolution and DAC1 is always enabled. The higher resolution is available with a new IOType in the low-level Feedback function, which the high-level UD driver uses automatically. This causes the DACs to have more noise when the timer clock is decreased from the default of 48 MHz, so there is a compatibility option available in LJControlPanel to use 8-bit DACs.
• On the U3-HV only, the first four flexible I/O are fixed as analog inputs (AIN0-AIN3), and have scaling such that the input range is ±10 volts normally, and +20 to -10 volts when using the “Special” range. The input impedance of these four lines is roughly 1 MΩ, which is good, but less than the normal low voltage analog inputs. Analog/digital configuration and all other digital operations on these pins are ignored. FIO4-EIO7 are still available as flexible I/O, same as the U3-LV.

Revision 1.20/21 U3s cannot be upgraded to 1.30.