The LoRa Developer Forum is now in read-only mode and new content will not be added.
Semtech, in its commitment to enhance user experience and streamline content, has successfully integrated the LoRa Developer Portal content into Semtech.com. As a result of this consolidation effort, the LoRa® Developer Portal Forum will be discontinued on May 1st. After this date, you will be automatically redirected to Semtech.com.
For any technical support related to LoRa, please feel free to reach out to our experts here. If you have sales inquiries, please contact us here.

FORUM

Series 1k ohm resistors on SPI lines

Semtech Transceivers
#1

The reference design for the SX1282 shows series 1k ohm resistors on the SPI bus lines. What are they for? What is their purpose?

#2

Series resistors in bus lines fulfill two purposes:

  1. they dampen signal ringing/overshoot.
  2. they limit cascading faults where one IC has a random hardware fault turning the SPI lines e.g. to short circuits to GND. The resistors in that case limit the current e.g. flowing out of the outputs of the microcontroller.

Be careful: the series resistors form a low-pass filter (RC) together with the input capacitance of the receiver pin (typically some pF). This limits the usable SPI clock rate.