The widespread module "MCP2515_CAN has only 2 connections, CANH and CANL. The CAN-GND required in all serious descriptions is missing. Isn't that necessary in hobby circles with its 20 cm long / short CAN buses?"
If you are asking "is a ground necessary in a system that uses differential drivers" here's a quote from a Texas Instruments application note https://www.ti.com/lit/pdf/snla049
"Although the potential difference between the data-pair conductors determines the signal without officially involving ground, the bus needs a ground wire to provide a return path for induced common-mode noise and currents, such as the receivers' input current. A typical mistake is to connect two nodes with only two wires. If you do this, the system may radiate high levels of EMI, because the common-mode return current finds its way back to the source, regardless of where the loop takes it. An intentional ground provides a low-impedance path in a known location, thus reducing emissions."
There is also the issue of receiver common mode voltage limits so you need to make sure that your grounding scheme design doesn't cause problems.
I don't think I have ever seen a hobby grade anything that has a sticker that shows it has passed any kind of EMI testing.
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Hello Rudolf,
Could you take a look to this link ?
Pi Pico SPI issues
I have opened a new PI PICO SPI thread as the one you opened in April is closed.
Ich danke dir im Voraus
Mit freundlichen Grüßen
Hello Jenrique,
I used your sketch with a MCP4921 (12 bit) and unfortunately only get 55 Hz. But you have now received a lot of good advice. I will therefore continue to pursue SPI now.
I'm using Earle F. Philhower's package, which seems to be more efficient than the mbed-based Arduino package.
With regards / mit freundlichem Gruß
Rudolf Schenke
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