Texas Instruments BUF22821 Evaluation board BUF22821EVM-USB BUF22821EVM-USB Datenbogen
Produktcode
BUF22821EVM-USB
V
=
DAC_CHANNEL
15 V x 68
1024
= 0.996 V
BUF22821EVM-USB Software Overview
For example:
Channel 6: Code 44 (hexadecimal) = 68 (decimal)
(4)
6.2.3
Read DAC Button
By pressing the Read DAC button in the BUF22821EVM-USB software, all of the BUF22821 DAC
registers are read to obtain the respective current register contents. Once the read procedure is complete,
all of the corresponding text boxes are updated to show the current values present in the DAC registers.
registers are read to obtain the respective current register contents. Once the read procedure is complete,
all of the corresponding text boxes are updated to show the current values present in the DAC registers.
6.2.4
Write DAC Button
The method used to write the values in the DAC registers is based on whether or not the Auto Write
feature is enabled. The BUF22821 has two methods of writing information into the DAC registers. The first
method allows for the output voltage to change immediately after the writing to the DAC register. In the
BUF22821EVM-USB software, this mode is configured by enabling the Auto Write feature found in the
Buffer Menu drop-down menu. In this mode, as an individual channel is written to, the output voltage
changes as soon as the user moves to a different text box in the software.
feature is enabled. The BUF22821 has two methods of writing information into the DAC registers. The first
method allows for the output voltage to change immediately after the writing to the DAC register. In the
BUF22821EVM-USB software, this mode is configured by enabling the Auto Write feature found in the
Buffer Menu drop-down menu. In this mode, as an individual channel is written to, the output voltage
changes as soon as the user moves to a different text box in the software.
The second method of writing to the DAC registers allows for the user to write multiple channels and then
have all of the output voltages change at the same time, rather than each channel voltage changing as
soon as it is written to. Disabling the Auto Write feature in the software allows the user to enter all of the
desired values for all of the channels, and then press the Write DAC button to change all of the output
voltage of all of the channels at one time. When the Auto Write feature is enabled, no change occurs to
the output voltages when the Write DAC button is pressed. This action occurs because after the text box
for a given channel has been updated, as soon as another item in the software is clicked, the Auto Write
feature automatically performs a write command to the updated channel that then updates the output
voltage. When in the Auto Write enabled mode, the Write DAC button cannot be pressed with data in the
corresponding channel text boxes that are different than the values already stored in the DAC register; no
change to the DAC registers will occur.
have all of the output voltages change at the same time, rather than each channel voltage changing as
soon as it is written to. Disabling the Auto Write feature in the software allows the user to enter all of the
desired values for all of the channels, and then press the Write DAC button to change all of the output
voltage of all of the channels at one time. When the Auto Write feature is enabled, no change occurs to
the output voltages when the Write DAC button is pressed. This action occurs because after the text box
for a given channel has been updated, as soon as another item in the software is clicked, the Auto Write
feature automatically performs a write command to the updated channel that then updates the output
voltage. When in the Auto Write enabled mode, the Write DAC button cannot be pressed with data in the
corresponding channel text boxes that are different than the values already stored in the DAC register; no
change to the DAC registers will occur.
shows the location in the Buffer Menu with the Auto
Write feature enabled. Click the Auto Write feature again to enable/disable the feature, depending upon its
current state.
current state.
Figure 20. Auto Write Feature Enabled
20
BUF22821EVM-USB Evaluation Board and Software Tutorial
SBOU117
–
September 2011
Copyright
©
2011, Texas Instruments Incorporated