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Tool/software:
Hello,
I would like to read as many as possible spi sensors using tm4c1294.
I understand the microcontroller has 4 spi buses.
I also understand that using the extra 2 data lines in QSSI mode for independent SPI devices is not possible as illustrated in https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1177186/tm4c1294ncpdt-using-qssi-to-gather-data-simultaneous-on-3-spi-data-lines
How could I go about maximizing read capacity of each bus? could I just not use the provided FSS from the bus, and use a GPIO to chipselect the SPI device to be read?
Are there any ti products like bus multiplexers to ease the design of this circuit.
I am also interested on multiplexing I2C lines.
Best Regards,
Can
Hi Can,
The post you referred as well as the one I just answered you https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1407425/tm4c1294ncpdt-qssi-advanced-mode, you cannot use the QSSI mode to access multiple independent SPI devices at the same time.
How could I go about maximizing read capacity of each bus? could I just not use the provided FSS from the bus, and use a GPIO to chipselect the SPI device to be read?
For legacy SPI mode (using only MOSI and SIMO) or the advance mode, you can use a GPIO instead of Fss for chip select. For example, if you have three SPI devices then you can use three GPIO signals to control each SPI device with one SPI master instance. For writes, the TX pin can be common to all SPI devices but you need to consider the loading on the bus. For reads, you need to multiplex the three slave inputs. Since these inputs are digital signals you can visit the digital multiplexer/encoder product page at https://www.ti.com/switches-multiplexers/digital-multiplexers-encoders/overview.html.