This guide is meant to explain how to upgrade the the ClearFog Base to support both CN9130 SOM and A388 SOM.
Remove the components from table below:
# | RefDes | Qty | Action | Comments |
1 | R153 | 1 | Remove | RES 740ohm |
2 | U24 | 1 | Remove | 74LVC1G125GW |
3 | U26 | 1 | Remove | 74LVC1G125GW |
The components locations are marked green in the pictures below:
The changes outlined partially impact functionality of the M.2 connector:
pin 6 (FULL_CARD_POWER_OFF#) is left floating
pin 67 (RESET#) is left floating
If an M.2 module is missing internal pull-ups, or has internal pull-down, it might permanently stay powered off or in reset.
As a workaround the IOs originally controlling the operational amplifiers U24 / U26 can be connected directly to M.2 connector using short wire, as shown below:
Some LTE modules were found to have integrated pull-down for FULL_CARD_POWER_OFF, therefore the following workaround is recommended:
RESET is specified as a 1.8V signal for M.2, digital IO has 3.3V logic level.
Therefore no workaround is recommended.
If strictly required, operation may be safe in open-drain configuration as long as software behaviour is validated first.