DOC: SPII2CHDWBrief - V2.71 07/25/2017
PAGE 4
NOTICE
Important Notice:
LadyBug LB5900 Devices operating in SPI and I2C modes differ in several ways from traditional
SPI & I2C devices. It is important to understand some of these differences to have a successful
implementation of the system.
Due to familiarity to memory and other chip based devices, the user may expect the response
time to be the same after each request. The LB5900 Sensor’s SPI & I2C engine is dependent on
the sensor’s primary processor. The time required for each request will vary significantly with the
request. Further, the time required to make measurements may depend upon the power level
and other factors.
Sensor Firmware updates. When the sensor is updated, the time to process commands may
change. Additional features may cause certain commands to require more time for completion,
this includes existing commands that may appear to be unrelated.
Adherence to the following list of recommendations will assure success.
-
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Connect Pin 1, SPI/I2C Select, directly to power or ground. Do not connect it to a
control line. This line is tested at power up only; and any startup glitches on the controller
may cause erroneous selection that can only be cleared by power down.
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Prior to sending commands or queries, test the sensor to make sure it is ready.
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Adhere to the timing recommendations and do not clock data faster than the
recommended rates, even though the sensor may perform well at faster rates and
reduced setup times. This will assure that future firmware versions will operate properly.
-
Do not test the sensor to determine if it is ready for a command or query faster than the
recommended minimum time (1ms). Bear in mind that each request interrupts the
processor to fulfil the request.
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Avoid unnecessary requests after sending measurement commands. For example if a
measurement is expected to take 100ms, request readiness after 90ms, or at 5 or 10ms
rather than 1ms.
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If a measurement is in process, do not send the sensor anything other than a test to see if
the measurement is complete or to send
●
a DCL command.
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Read the REVISIONS & UPDATES Section each time this manual is updated. Important
changes are marked with
●
or
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