Adafruit MAX31865 is not sending data

_jarek_ · Joined: 06 Aug 2014 Posts: 5

You wrote down the configuration, and have you tried to read it and check if it is sure that SPI is working?

murmel · Joined: 13 Oct 2014 Posts: 17

Hello Przemek,

what is meant by PoR?

Regards
Murmel

programmista123 · Joined: 31 Jan 2018 Posts: 141

Hi,

It's Power-On Reset.

Regards,
Przemek

murmel · Joined: 13 Oct 2014 Posts: 17

Thanks!!!

murmel · Joined: 13 Oct 2014 Posts: 17

@programmista123
which address should I read?

Greetings
Murmel

MWS · Joined: 22 Aug 2009 Posts: 2262

He seens to tell you to do your readouts only after you power on the whole circuit.

After powering on obviously it is a POR, in contrary to a reboot by code failure, brown out, jump to 0, or watchdog reset.
The case of reboot can be found out by reading MCUCR/MCUCSR, in case of Bascom controller register R6, but this seems unimportant for this purpose.
It may help to blink a LED at startup to detect undesired reboots.

EDC · Joined: 26 Mar 2014 Posts: 971

I think MCU power on reset is not the case here.
We talking about MAX PoR.

You can read showed registers and print them.
Like is shown in the picture addresses from&H00 to &H02 should have zeros but &H03 and &H04 should give you the result of &HFF.

So you can also write something to the &H80 address and then read it back by reading &H00
You should get the same value.

MWS · Joined: 22 Aug 2009 Posts: 2262

murmel · Joined: 13 Oct 2014 Posts: 17

Hello EDC,

Reading out the addresses 01h, 02h, 03h and 04h always resulted in 7Fh (127). No config word was sent.

@MWS Unfortunately I can't work on the project every day, so there are always breaks until the next answer. I have to admit that, unlike you, I'm not an expert when it comes to Bascom. That's exactly why I'm happy about people like EDC and Przemek who offer their help without complaining.

Greetings
Murmel

EDC · Joined: 26 Mar 2014 Posts: 971

Now we find the cause.... Very Happy

For SPI to be in MASTER MODE its SS pin MUST be configured as OUTPUT nomather what because if this pin is set low externally then uC will switch SPI back into SLAVE MODE. This will be done only if pin SS is an INPUT. Characteristis are the readings then ... 127 Very Happy

You can use PORTB.4 for anything you want and it not must be used as CS (SS) but it must be used in OUTPUT MODE.

You use PORTB.2 on Mega32 for CS and this is the port of SPI so I fistly think that this is a proper SS pin (this is true for Mega328P). But today I look into datasheet and saw this ... Very Happy

Please config PORTB.4 as output and then test again Wink

MWS · Joined: 22 Aug 2009 Posts: 2262

EDC · Joined: 26 Mar 2014 Posts: 971

I joined to this topic little late and when I saw that, after many replies, problem persist then I maybe dont read them all carefully enough Wink

I know that niuanses about SS Input/Output but dont want to elaborate about everything so I wrote it simple.

I think that my picture will be more than thousants of words for that user and finally solve his problem.

MWS · Joined: 22 Aug 2009 Posts: 2262

murmel · Joined: 13 Oct 2014 Posts: 17

Hello EDC,
I defined the SS pin as the output and placed it across the pullup resistor to 5V.
The result is Rtd_h = 0 and RTD_l =0. The CS pin of the MAX is connected to PinB.2.
Here is the code:

'**************************************************************************************************
' Programmcode z.T. von H.Kipnik https://www.roboternetz.de/community/archive/index.php/t-75139.html
'
' https://www.analog.com/media/en/technical-documentation/data-sheets/max31865.pdf
'**************************************************************************************************

$regfile = "m32def.dat" ' CPU
$crystal = 16000000 ' Frequenz
$baud = 19200 ' use baud rate
$hwstack = 80 ' HW stack
$swstack = 80 ' SW stack
$framesize = 80 ' Frame space

Config Lcd = 20x4
Config Lcdpin = Pin , Db4 = Porta.4 , Db5 = Porta.5 , Db6 = Porta.6 , Db7 = Porta.7 , E = Portc.7 , Rs = Portc.6
Config Lcdbus = 4
Cursor Off : Cls

Config Portb.1 = Output ' Backlight LCD
Portb.0 = 1

Config Portb.2 = Output ' CS for MAX31865
Max_cs Alias Portb.2
Max_cs = 1

Config Portb.4 = Output ' SPI Master on
Portb.4 = 1

Waitms 500

Config Spi = Hard , Interrupt = Off , Data_order = Msb , Master = Yes , Polarity = High , Phase = 1 , Clockrate = 128 , Noss = 0

Spiinit

Dim Rtd As Integer 'Integer
Dim Rtd_l As Byte At Rtd Overlay
Dim Rtd_h As Byte At Rtd Overlay + 1
Dim Temperatur As Single 'Single
Dim Write_address As Byte
Dim Read_address_1 As Byte
Dim Read_address_2 As Byte
Dim Max_31865_config_register As Byte ' config register

Write_address = &B10000000 ' Config writeaddress
Read_address_1 = &B00000001 ' RTD_h Read Address
Read_address_2 = &B00000010 ' RTD_l Read Address

Max_31865_config_register = &B11100011 ' MAX-configuration

Max_cs = 0
Spiout Write_address , 1 ' write config register
Spiout Max_31865_config_register , 1
Max_cs = 1

'***************** Mainloop *********************
'(

Max_cs = 0 ' read Highbyte MSB
Spiout Read_address_1 , 1
Spiin Rtd_h , 1
Max_cs = 1

Max_cs = 0 ' read Lowbyte LSB
Spiout Read_address_2 , 1
Spiin Rtd_l , 1
Max_cs = 1
')
Do
Max_cs = 0
Spiout Read_address_1 , 1
Spiin Rtd_h , 1
Spiin Rtd_l , 1
Max_cs = 1

Shift Rtd , Right , 1 ' 16bit -> 15Bit

Temperatur = Rtd / 16 ' Temperature calculation
Temperatur = Temperatur - 256
Locate 1 , 8
Lcd " "
Locate 2 , 8
Lcd " "
Locate 3 , 8
Lcd " "
Locate 4 , 6
Lcd " "
Locate 1 , 1
Lcd "RTD_h: " ; Rtd_h
Locate 2 , 1
Lcd "RTD_l: " ; Rtd_l
Locate 3 , 1
Lcd "RTD : " ; Rtd
Locate 4 , 1
Lcd "Temp: " ; Temperatur

Waitms 500
Loop[code]

Greetings
Murmel

EDC · Joined: 26 Mar 2014 Posts: 971

Please take a one step back.
If you have proper SPI config then try it first.
Set address to Config_write &H80 and write it with config value.
Then set address to Config_read &H00 and read this config back.
Then LCD it and values should match.