We had a project where we using the LMP90100 to measure the scale through a load cell. We connect the micro-controller to LM90100 by the SPI interface, unfortunately we had connected the CSB to ground.
Now when we turn on the power there are 2 different results.
- The communication is working fine, we got fine resolved and stable ADC output.
- The communication to the LMP90100 is not working at all. Looking at the SCLK pin using a oscilloscope we saw that at power up, there is a rising edge there (false one, not intended but we have no way to eliminate it now); that false CLK makes all subsequent transfer wrong.
Now we need a way to reset the SPI communication engine of the LMP90100 but find no measure (Actually there is one described in the datasheet by sending >= 73 consecutive "1" bit but that feature is disabled by default).
Your suggestion is appreciated.
PS. The description on Register reading is confusing where the INST1 byte was described as: 0x10 = write address; 0x90 = read address but actually the 0x90 code is never used.
Hi Long Tran,
We are aware of this issue. False edge on SCLK from the SPI master(mcu) can be solved in most of the mcu's by making the I/O on which SCLK will become active to be high/low by pullup/pulldown internally and should be same as the SPI idle condition and should be done before SPI is enabled.
Which mcu are you using?
Thank you for your quick response! We use the Microchip's PIC18F4523.
I've just decided to cut the CSB out of GND and connected it to a MCU pin. It's working fine now.
With best regards,
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