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Hi. I am designing a board with the TMS320F28335 MCU and have a question about the serial communications interface (SCI).
I have looked at the GPIOs of the TMS320F28335 datasheet and it seems that there are multiple GPIO pins on the F28335 that can be configured as Tx/Rx pins for SCI (Serial Communications interface). For example, GPIO29 and GPIO 35 can both be configured for ‘SCI-A transmit’. Could someone please tell me which pins I should use to connect the RS485 transceiver to, if there is any preference? It should be noted that serial communication will be used to program the onboard flash memory of the microcontroller and to communicate with PLCs in the field.
I also would like to know what isolated power supply I should use for the transceiver ISO15 (http://www.ti.com/product/iso15/description), for the bus side of the chip. IT needs a 3.3V isolated supply.
Rohit,
Functionally, there is no difference between one GPIO pin or the other. i.e. you could use any GPIO pin to act as SCITXA. This is completely determined by the constraints of your application. Even though there are many peripherals (and multiple instances of peripherals) on the chip, the peripheral-mix needed in an application typically constrains the choice of GPIO pins for a particular application.
I will get back to you on the isolated power-supply question.
Hi Rohit,
SN6501 should suffice your need. In case you see a need for higher current on the isolated power supply, you could also have a look at SN6505A or SN6505B. All these device datasheets include a good list of transformers that can be used as reference while choosing a transformer for specific power rail requirements.
Regards,
Koteshwar Rao