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LM95071: Microprocessor interface Bidirectional Data Pin

Part Number: LM95071
Other Parts Discussed in Thread: LM71, TMP122

I am looking at this part, and see the datasheet diagrams and the attempt to explain how to connect to microprocessors. 

In addition, I see the post in the forum with the headline "LM95071: Interfacing LM95071 with PIC microcontroller via SPI"  

However, this is not clear to me how to interface with a microcontroller's standard SPI ports.  I.e. not GPIO, but ports assigned to an SPI module in the micro, and with other SPI devices on the same pins. 

SPI is designed to have a MISO, MOSI, and CLK pins.  The master chip selects the slave device with the CS pin (often GPIO), transmits commands to the slave on the MOSI pin, and receives data back from the slave device(s) on the MISO pin.  Now that I've stated the obvious details of the SPI physical implementation, I now suggest that the TI explanation for how to connect to your device is not so obvious.  No where do you show how to connect to a "standard" SPI port.

Figure 1 shows a Microwire interface (and not labeled clearly as such).  This is not applicable to my situation.

Figure 14 shows an Intel 196 processor with TX pin acting as the clock, and the RXD pin sending and receiving.  I'm not sure how you would get the RXD pin to also transmit, and how you would put a clock on the TX pin without bit banging, but I don't use that processor, I can't really comment.  But this is not helpful in my situation. 

Figure 15 shows an HC11 processor with some GPIO pins and feeding the bidirectional pin into the MISO pin. My assumption here is that the GPIO is providing the data (command) output from the HC11 by bit banging (otherwise wouldn't the MOSI pin be shown in the figure?) However, why is does the GPIO pin have a serial 10k resistor?  Usually you put a 47Ohm resistor.  10k would slow down the edges....

In short, the datasheet does not explitly define how to connect to a standard Microprocessor SPI port (even TI's own microprocessors), and I can't understand why? For instance MSP432 processor has the PM_UCA1SIMO Slave in, master out, the Slave out, master in – PM_UCA1SOMI, the Slave transmit enable PM_UCA1STE, and Clock signal output - PM_UCA1CLK.  How to connect to that micro? 

I don't want to fuss with special firmware I like TI's parts, but this is making me want to choose the Analog Devices sensor ADT7301, which has MOSI MISO ports. 

  • First of all, let me apologize that we don't have a very big SPI portfolio of temperature sensors. Due to the temperature range of a semiconductor temperature sensor, most applications are in consumer products where I2C is preferable. If you would consider I2C, (which MSP432 supports) you would have access to a much wider range of higher accuracy, lower cost, and lower power products with a standard interface.

    That said, all of our SPI products have this bidirectional pin that has frustrated you. Other notable examples include LM71 and TMP122. This pin is both MOSI and MISO at the same time. You must short them together. For the first 16 clock cycles, you must disable the output of your MOSI and receive temperature from the slave device. After these 16 clock cycles, if you wish to change configuration of the slave device, you must enable your MOSI driver and provide 16 clock cycles of input data. If you have no desire to change the default settings of the device, you may leave your MOSI disconnected and use only MISO to receive temperature data.

    Ren