Hello Koepel,
thank you for your comments.
I'm attaching a picture where 3 scenarios that I've tested are shown.
Scenario A :
- MKR 1010 fitted in Edge slot for MKR1
- In the Edge running program, power lines 3V3, 5V and MKR1 are enabled
- Voltmeter measuring V between VCC and GND pins of MKR 1010
*I2C slave accelerometer board connected to MKR1010 pins (scl,sda,vcc,gnd)
Scenario B:
- Empty Edge slot MKR1
- In the Edge running program, power lines 3V3, 5V and MKR1 are enabled
- Voltmeter measuring V between VCC and GND pins of MKR1 slot
- I2C slave accelerometer board connected to MKR1 slot pins (scl,sda,vcc,gnd)
Scenario C:
- Empty Edge slot MKR1
- In the Edge running program, power lines 3V3, 5V are enabled; MKR1 is disabled
- Voltmeter measuring V between VCC and GND pins of MKR1 slot
- I2C slave accelerometer board connected to MKR1 slot pins (scl,sda,vcc,gnd)
Electrical Findings
Scenario A:
- measured VCC voltage is 3.3 Vdc
- I2C slave accelerometer LED fully bright
Scenario B:
- measured VCC voltage is 1,8 Vdc
- I2C slave accelerometer LED dimmed
Scenario C:
- measured VCC voltage is 0 Vdc
- I2C slave accelerometer LED is off
SW Findings
Only scenario A permitted the program running in the Edge cpu to be successful in getting data from the I2C slave but only if the MKR1010 cpu is also running a program that uses I2C comms; in this situation, if the program running in MKR1010 cpu is changed to another empty program or one that doesn't use I2C comms, followed by an Edge reboot, then the Edge program is no longer successful in I2C comms.
To regain I2C successful comms by the Edge, then a program using I2C has to be downloaded to MKR 1010 followed by an Edge reboot
These were my findings so far - and I'm a bit puzzled, or just a newbie 