Hi,
The compass has been a bit of a puzzle. Sometimes the AK8963C popped, so the SPI SO failed or went to a lower voltage, and I tried a level shifter as a buffer. This has worked for some modules, but on farther investigation, I found, what should be a PIC input, is actually outputting. I presume this has been what popped the AK8963C module outputs.

I cut the AK8963C SPI SO track and checked with a scope. Here are 2x pics, showing the output from the AK8963C and the signal from the PIC input.

Can anyone shed light on how to stop the PIC from outputting, please?

Camerart

 

hi,
Check that this is not a solder bridge.?
E

 

hi,
Check that this is not a solder bridge.?
E
View attachment 197070

Hi E,
It's not a bridge, and I have other boards, that give the same signals.
C.

 

Hi,
The compass has been a bit of a puzzle. Sometimes the AK8963C popped, so the SPI SO failed or went to a lower voltage, and I tried a level shifter as a buffer. This has worked for some modules, but on farther investigation, I found, what should be a PIC input, is actually outputting. I presume this has been what popped the AK8963C module outputs.

I cut the AK8963C SPI SO track and checked with a scope. Here are 2x pics, showing the output from the AK8963C and the signal from the PIC input.

Can anyone shed light on how to stop the PIC from outputting, please?

Camerart

I don't think PIC is outputting, if the data direction is not changed in the middle of the program, but the other peripherals connected to MISO are.
Check the chip selects.They may be on at the same.

 

I don't think PIC is outputting, if the data direction is not changed in the middle of the program, but the other peripherals connected to MISO are.
Check the chip selects.They may be on at the same.

Hi J,
I checked the chip selects, and think they're ok. I've added the latest program version, in case anyone wants to check.

Here are two Scope shots. (I added a buffer between the AK8963C output, and the board output MISO)
'MISO connected' one shows:
Top AK8963C output into the buffer.
Bottom MISO after buffer, connected to the PIC.

When MISO is disconnected between the board and the PIC the board MISO shows 3.3V

'MISO Disconnected' shows:
Top, the Board MISO output
Bottom The disconnected PIC MISO.

Camerart

 

Hi,
Looking at MISO disconnected in #545, is it possible to tell how far down the program the bottom DATA pulse would be?
C

 

Hi,
I commented out [ ALTMTR = 0 and ALTMTR = 1 ] from both sections under 'READ BMP280'

(MISO Disconnected) The bottom signal from the MISO disappeared

(MISO Connected) The bottom MISO signal from the board is still being suppressed to a lower voltage.

I've written to Vladimir!
C

 

Cut everything connected to MISO and look the pin with the scope.

Edit: deleted an erranous sentence.

 

Cut everything connected to MISO and look the pin with the scope.

Edit: deleted an erranous sentence.

Hi J,
Regarding the deleted sentence. I shortened the
Define STRING_MAX_LENGTH = 50 '70XXXXX
while testing, but later I think I can shorten the length.

With the MISO disconnected from all peripherals, there is no Scope signal. It seems that the BMP280 is generating the ( MISO Disconnected BOTTOM signal).

I tried a resistance check between the disconnected MISO wire and GND = 12MOhm.

Connecting the MISO to only the compass, suppresses the Compass output to the lower voltage as before.
C

 

Hi,
Here is a PDF, which may be of interest.

It's a bit advanced for me, but looking through it, especially 9.4, I can see a possible answer to the MISO outputting problem.
C

 

Hi,
I'm not a programmer, but thought I'd try adding the ASM from the #550 Data sheet, to see if it does anything, but I got errors.
Here's a screen shot.
C

 

hi C,
How have you defined 'rp0' also it should be 'mov wv trisc', so how is 'wv' defined.?

Post the full asm code listing.
E

 

hi C,
How have you defined 'rp0' also it should be 'mov wv trisc', so how is 'wv' defined.?

Post the full asm code listing.
E

Hi E,
I'm following the code listing in the PDF at #550 9.4 PORTC. PORT C should be set to %10010000.
C

 

hi,
One point you have typed an error.

 

hi,
One point you have typed an error.

View attachment 197878View attachment 197879

Hi E,
Thanks, now there's only one error.

I'm using an18LF4620 PIC
C

 

hi,
Read this link for rp0 explanation.
https://www.microchip.com/forums/m499306.aspx

E

 

hi,
Read this link for rp0 explanation.
https://www.microchip.com/forums/m499306.aspx

E

Hi E,
I have read through it a couple of times, and can see that 18 series PICs don't have RP0 RP1, but I don't know what to put instead of the [ ASM: bsf status,rp0 ] line.
C.

 

hi,
This clip is from the 18LF4620 d/s

 

hi,
This clip is from the 18LF4620 d/s
View attachment 197889

Hi E,
I see, a simpler method, without the STATUS line. It compiles, with no errors, so I'll test it.

EDIT: It didn't make any difference. Once the PIC MISO is connected to the AK8963C MISO, the DATA voltage drops down to App 1.65V, so doesn't work.
Thanks, C.

 

hi,
Also note as you are using other peripherals.
E