Multiple SPI slaves

Projects Networking, Protocols, and Devices
1

Hey all!

Having some troubles with multiple SPI slaves.
My sketches run great if I only use TFT and MCP2515 or TFT and MAX6675.

But if I run the trio, the max6675 blocks the SPI bus.
They all are connected on the same SPI(miso,mosi,clk)

Already tried to set the cs pins as outputs and going HIGH;going LOW,
but doesn't work.

Can someone give me a good hint?

Hardware used:
Arduino Pro
MCP2515
1.8 TFT
MAX6675

CS pins:
TFT pin10
MCP2515 pin 5
MAX6675 pin 6

2

Try to analyze the CS pins logic levels when you have the 3 connected.It can be only one device active at a time so perhaps in your code or library you are using it could be left the CS pin active, then try to send a message and does nothing.It would be wonderful if you have a logic analyzer to debug that ...
Without it a scope would be helpful.
Happy codding

3

I don't have a scoop or a LA.
What do I need to check in the libraries files?

Can't I just "over rule" the libraries, with some extra coded lines?
Like defines some pins as outputs and declare them high or low?

4

You shouldn't need to "over rule" the libraries. Post the code that fails.

Have you tried the MCP2515 and MAX6675 together without the TFT display?

5

Problem solved by switching from the max6675 to max31855 library!

Thx!! :slight_smile:

6

Are you certain this is not D5?

MCP_CAN  CAN0(5); // Set CS to pin 10

First thing you should do is disable all slave SPI device interfaces. I used variables for the CS pins maxCS, mcpCS, and tftCS below. Assign them pin numbers by #define.

void setup()
{
  Serial.begin(115200);
  
  pinMode(maxCS,OUTPUT);
  digitalWrite(maxCS,HIGH);

  pinMode(mcpCS,OUTPUT);
  digitalWrite(mcpCS,HIGH);

  pinMode(tftCS,OUTPUT);
  digitalWrite(tftCS,HIGH);