Q: Weak edges over SPI data lines I am developing a driver for an SPI temperature sensor, and having some trouble with poor quality edges near the end of packet on the data lines.
While I am not experiencing any data loss, I am worried this is evidence of a larger issue; any suggestions on potential simple causes of this problem would be welcome.

Temperature Sensor Data Sheet
https://datasheets.maximintegrated.com/en/ds/DS1722.pdf

A: As you can see in this table from the datasheet, as soon as the Chip Enable signal goes low, the output of the slave goes into High-Z state until a read operation is initiated.

Then the output is essentially floating, so the voltage on the line is then determined by some pull up/down if present, or simply by any leakage current on the in/output.
Either way, the voltage on the MISO/MOSI lines really does not matter between the packages sent. So this behavior is both expected, and not an issue.

A: You need pull-up resistors. It's a bad idea to drive CMOS inputs with a floating voltage. The resistors can be relatively large, e.g. 50-500kOhm, so as not to waste power. The signals will then look reasonable. Remember that a scope probe is 10MOhm, so with a 500k pull-up, you'll see voltage 5% smaller than it is without the probe load!
