UG-1921
Rev. 0 | Page 10 of 18
AUTOMATIC CHIP RESET
If a reset of the
chip is required on the
ADMV8818-EVALZ, click
Reset Chip
(see Figure 7 and
Label J3 in Table 1 for additional information). This automated
sequence performs the following actions:
•
Toggles all
general-purpose input/output (GPIO)
logic pins to a low state, which brings the RST pin low to
initiate a hard reset of the ADMV8818.
•
Toggles the RST pin high to bring the ADMV8818 chip
back to the normal operating state.
•
Programs Register 0x000 to 0x81, which also resets the
ADMV8818. This step covers legacy boards that did not
have the RST pin connected.
•
Programs Register 0x000 to 0x3C to enable the SDO pin
on the ADMV8818 and to allow SPI streaming with
Endian register ascending order.
•
Reads back the register settings of the ADMV8818.
LOSS OF BOARD COMMUNICATION
When the ADMV8818 is turned off and then on, or if the USB
cable is disconnected and connected while the
software is
running, communication with the ADMV8818 may be lost. To
regain communication, take the following steps:
1.
Click the
System
tab.
2.
Click the USB symbol in the
SDP-S Controller
subsystem.
3.
Click
Acquire
.
If this action does not work, restart the ACE software to
reinitiate communication with the ADMV8818-EVALZ.
REGULATOR BYPASS
The ADMV8818-EVALZ has a negative voltage generator and
three LDO regulators on board that allow the user to operate
using the 5 V USB supply voltage from the PC via the SDP-S.
These on board LDO regulators provide the three necessary
supply voltages, −2.5 V, 2.5 V, and 3.3 V. If desired, these LDO
regulators can be bypassed by removing the 0 Ω resistors (R23,
R26, and R32) from the ADMV8818-EVALZ, and then applying
each voltage independently by using the corresponding test points.
Bypassing the on board regulators is useful for measuring the
ADMV8818 supply current, but it must be noted that each
supply pin is also connected to status indicator LEDs, DS1 to
DS3, and each LED draws approximately 2 mA of current.
Remove the R2, R3, and R90 resistors to disable these status
indicators. See Figure 10 for more details.
PLUGIN SPI REGISTER CONTROLLER
The ADMV8818 plugin utilizes an SPI register controller to
communicate with the ADMV8818. When using the
ADMV8818 in a system, it is recommended to follow a similar
methodology for implementing SPI communication. The
following is a summary of the SPI register controller:
1.
Determine if Register 0x000 is not set to a value of 0x3C.
2.
If Step 1 is true, set Register 0x000 to a value of 0x3C to
enable the SDO pin on the ADMV8818 and allow SPI
streaming with Endian register ascending order.
3.
Determine if the values have changed for any of the WR
registers (Register 0x020 to Register 0x029).
4.
If Step 3 is true, write Register 0x020 to Register 0x029 by
pointing to Register 0x020 and streaming out 10 bytes of
data. The transaction is 96 bits in total (R/W bit + 15 address
bits + 80 data bits). Streaming out the data in this order
ensures that the switch position priority is WR0 to WR4.
5.
If Step 4 has occurred, write dummy data to Address 0x0A.
Note that Address 0x0A does not exist in the ADMV8818,
and the written dummy data is ignored. This step is
microcontroller architecture dependent and can be
ignored in most cases. It is necessary for the SDP-S to clear
the SPI bus and reconfigure for a standard 24-bit SPI
transaction.
6.
Determine if the values have changed for any of the LUT
registers (Register 0x100 to Register 0x1FF).
7.
If Step 6 is true, write Register 0x100 to Register 0x1FF by
performing the following:
•
Pointing to Register 0x100 and streaming out 64 bytes
of data.
•
Pointing to Register 0x140 and streaming out 64 bytes
of data.
•
Pointing to Register 0x180 and streaming out 64 bytes
of data.
•
Pointing to Register 0x1C0 and streaming out 64 bytes
of data.
8.
If Step 7 has occurred, repeat Step 5.
9.
Write out any remaining registers that may have changed.
