WIZ550io + IOShield A + Arduino M0 USB issue

Question

When I connect the USB to the Arduino M0 with shield A (ver 1.1) and WIZ550io, the M0 USB port is not recognized in my Linux OS. When I remove the shield The USB port is recognized correctly. I have tested several Arduino M0 and M0 pro boards. This is the same with or without the WIZ550io network module connected to the shield, so looks like a shield issue. Is the shield supported on an M0, if it needs modifying what do I need to do? Thanks W Syslog with shield: May 3 14:03:46 wk kernel: [7223926.193746] usb 2-1.6: >new full-speed USB device number 119 using ehci_hcd May 3 14:03:46 wk kernel: [7223926.265705] usb 2-1.6: >device descriptor read/64, error -32 May 3 14:03:46 wk kernel: [7223926.441656] usb 2-1.6: >device descriptor read/64, error -32 May 3 14:03:47 wk kernel: [7223926.617649] usb 2-1.6: >new full-speed USB device number 120 using ehci_hcd May 3 14:03:47 wk kernel: [7223926.689600] usb 2-1.6: >device descriptor read/64, error -32 May 3 14:03:47 wk kernel: [7223926.865566] usb 2-1.6: >device descriptor read/64, error -32 May 3 14:03:47 wk kernel: [7223927.041523] usb 2-1.6: >new full-speed USB device number 121 using ehci_hcd May 3 14:03:47 wk kernel: [7223927.449357] usb 2-1.6: >device not accepting address 121, error -32 May 3 14:03:47 wk kernel: [7223927.521440] usb 2-1.6: >new full-speed USB device number 122 using ehci_hcd May 3 14:03:48 wk kernel: [7223927.929230] usb 2-1.6: >device not accepting address 122, error -32 May 3 14:03:48 wk kernel: [7223927.929351] hub 2-1:1.0: >unable to enumerate USB device on port 6 Syslog without shield May 3 14:05:59 wk kernel: [7224058.870461] usb 2-1.6: >New USB device strings: Mfr=1, Product=2, SerialNumber=3 May 3 14:05:59 wk kernel: [7224058.870464] usb 2-1.6: >Product: Arduino M0 May 3 14:05:59 wk kernel: [7224058.870467] usb 2-1.6: >Manufacturer: Unknown May 3 14:05:59 wk kernel: [7224058.870469] usb 2-1.6: >SerialNumber: xxxxxxxxxxxxxxxxxxxxxxx May 3 14:05:59 wk mtp-probe: checking bus 2, device 124: “/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.6” May 3 14:05:59 wk mtp-probe: bus: 2, device: 124 was not an MTP device May 3 14:05:59 wk kernel: [7224058.871335] cdc_acm 2-1.6:1.0: >This device cannot do calls on its own. It is not a modem. May 3 14:05:59 wk kernel: [7224058.871348] cdc_acm 2-1.6:1.0: >ttyACM0: USB ACM device

wf2020 · Answer

Looked at the schematic, the fix is to cut off the IOREF pin on the shield. The IOREF pin, labeled +5V, is between the pin labeled J3 and the pin N_RESET. The Shield will receive 5V from the other pins labeled +5V. The 5V is down regulated to 3.3V so the Arm chip on the M0 is working as expected. The USB is now active and I have successfully loaded up the Ethernet2 WebServer example code. I suggest that if another version of this shield is produced that the IOREF pin is left unconnected. Thanks W