topic SPI waveform in Kinetis Microcontrollers

SPI waveform

kanimozhiraju — Fri, 16 Jun 2017 06:30:35 GMT

I sent you the spi waveform D0-sck,D1-mosi,D2-miso,D3-cs..I have attached waveform of mosi sck and cs.First i tr with 4mhz since my slave needs 4mhz but i was not able to see data its just oscillate.then i have changed clock and tried.The data is not getting written to slave.Thank you

Original Attachment has been moved to: screenshot-of-spi.rar

Re: SPI waveform

egoodii — Fri, 16 Jun 2017 12:36:28 GMT

I'm not sure what you did starting with pic VB8012-307EC97_2017-06-16_11-28-19.png, but it looks like you re-enabled 'continuous SCK', which isn't going to help ANYTHING. Turn that back off!

What I see in VB8012-307EC97_2017-06-16_11-13-54.png as your 2nd write, to register 0x20, BUT you must have done something different in your code as regards the CONT bit (other than what I have shown all along), because CS is only active for the first 3 bytes. Figure 2 in the AFE4490 datasheet clearly shows a full 32-bit CS (STE) requirement. Until you get that full-width CS, nothing else will ever work.

Re: SPI waveform

kanimozhiraju — Mon, 19 Jun 2017 10:34:55 GMT

hi egoodii‌,

I have attached the spi waveform since i have modified the code with what you have given me .Last two waveforms are concentrated on clk,miso and cs.Others are clk,mosi and cs.PCS is enable for 4bytes and while reading Miso is in zero state.I felt clk will be problem.Because if we use 4mhz or 8mhz waveform is not displaying in logic analyzer when i reduce the clock to 1 or .7mhz waveforms are displaying.I follow your suggestion and trying to progress in it.Thank you.

Re: SPI waveform

egoodii — Mon, 19 Jun 2017 10:45:34 GMT

I can't say what is going on with your scope's waveform sampling that it isn't showing you 4 or 8MHz, OR whether maybe your hardware has 'long unterminated traces', but in any case the waveforms you show look 'OK', except that now I don't see ANY activity on CS, so I don't know what you did to PCS controls to kill THAT off...

Re: SPI waveform

kanimozhiraju — Mon, 19 Jun 2017 11:01:45 GMT

hi egoodii‌,

The printf statements in realterm

data written to addrs 0
data written to addrs :4
data written to addrs :1
data read from addrs 0
data written to addrs 0
data written to addrs :4
data written to addrs :1
data read from addrs 0
data written to addrs 0
data written to addrs :4
data written to addrs :1
data read from addrs 0
data written to addrs 0
data written to addrs :4
data written to addrs :1

Re: SPI waveform

egoodii — Mon, 19 Jun 2017 13:51:51 GMT

The printf's don't tell me anything. Please try some new waveforms with CONT set for the first three bytes only, and PCS pattern set for all four.