SPI Hysteresis Not Working as Expected

Forum for discussing PicoScope version 6 (non-automotive version)
Post Reply
lpmay
Newbie
Posts: 0
Joined: Sun Nov 12, 2017 12:31 am

SPI Hysteresis Not Working as Expected

Post by lpmay » Sun Nov 12, 2017 12:41 am

Hi,

Just had a long struggle getting SPI decode to work. It seems like the hysteresis fields are not interpreted as expected. In the help manual, they are described as a band centered on the threshold. Sane values for this like 100mV around 1.5V on a 3V system do not work properly. However, an insane hysteresis value of 1.6V (greater than the threshold!) causes the scope to behave as if the threshold were 1.55V with a hysteresis band of 100mV and correctly decode. I strongly suspect that these hysteresis numbers are being interpreted as a second threshold, not hysteresis.

Any feedback on this issue I'm having is greatly appreciated. On a separate note, an enhancement to put both MISO and MOSI in the same SPI decoder so that MOSI and MISO could be compared in the same event table would also be great.

I'm using a 3406D MSO with PicoScope 6.12.9.2917 on Windows 7.

bennog
Active User
Active User
Posts: 33
Joined: Mon Nov 26, 2012 9:16 am
Location: Netherlands

Re: SPI Hysteresis Not Working as Expected

Post by bennog » Mon Nov 13, 2017 7:46 am

Can you post psdata file of what you are trying to accomplish ?

Benno

Martyn
Site Admin
Site Admin
Posts: 3333
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: SPI Hysteresis Not Working as Expected

Post by Martyn » Mon Nov 13, 2017 10:14 am

As requested, a data file would be good, we can then run it with debug software to see what values for hysteresis and threshold should be chosen.
On a separate note, an enhancement to put both MISO and MOSI in the same SPI decoder so that MOSI and MISO could be compared in the same event table would also be great.
This is already on the feature request list, not just for SPI but for all decoding.
Martyn
Technical Support Manager

Post Reply