Dennis Field / dvk-mx8m-bsb - History

Begin WiFi+BT M.2 socket circuit, connect the associated USB bus from the hub circuit, determined that the i.MX8M's UART's default POR state is such that CTS is an output and RTS is an input and assigned the signals accordingly

Begin USB 2.0 hub circuit for M.2 modules, remove supervisory/voltage monitor/watchdog circuit since the EmCraft SoM implements it

USB 2.0 hub circuit still needs to be completed.

Modify the boot config pins such that the eMMC is an 8-bit bus, depressing a momentary push button switch during boot causes SD boot, and relevant options

Use the main 18650 battery for the RTC (instead of a coin-cell), include information about which battery has been narrowed down to be the best option (NCR18650BD), remove 2K EEPROM used for the board ID (MAC address) since it won't be used

Have the charge controller IC handle the USB-C DRP PD switch mechanism, notes added on what procedure is required to operate as sink/source and how to swap between these roles

The mainline kernel's TCPM implementation needs to be used in conjunction with the charge controller IC's interface. For example, if the TCPC (PTN5110HQ CC controller) has the USB configured as a sink role then the TCPM (i.MX8M) would read out the CC_STATUS and POWER_STATUS registers of the CC controller IC to know this is the case, and then it (i.MX8M) would configure the charge controller IC accordingly (sink current from VBUS).

Both the CC controller and charge controller's open-drain output interrupt pins are tied together, which means if either of them pull the line low then the i.MX8M needs to check both of their fault registers to determine if a fault has occured on either chip. If the INT pin wasn't pulled low due to a fault then a status update event from either chip may have triggered it, which needs to be determined, as well as the corresponding action taken. These INT pins may need to be separated if the software side is too complex, so long as there's a spare interrupt pins available.

Fast swap is not supported, and is not a requirement.

Add USB type C circuit with DRP PD capability, should sink near 2A @ 5-6.5V and source 550mA @ 5V

Removed the reverse current protection circuit from the last commit due to the requirement changing to only 18650 battery and USB-C being possible power sources

Next thing to add is the charging circuit when the USB-C is in sink mode/role

Include reverse polarity protection circuit along with a simulation showing its effectiveness

Protecting VBAT from when board is sinking current via USB C. Protects against reverse polarity at the DC jack.

In EmCraft's instance VBUS should only be 5V when sinking current but they must protect against the condition when VBUS>12V and DC_IN=12V. This may need testing.

Move reference designators in the schematic so that they are legible

Use "Start to sheet number*100 and use first free number" designation, any new component added to the schematic will occupy the next available number in that sheet

For example: if sheet 2 has R201-R215 and we add a new resistor it will become R216.

Assign all associated signals to their respective pins on the EmCraft i.MX8M SoM

The ERC is now at the same state as the DART SoM schematic. Need to compare various aspects of the current schematic against the EmCraft reference design. The main buck-boost will likely need to be switched to a 5V regulator, or be configured to output 5V.

A regulator will likely need to be added which will output some VBAT voltage level (3.5~4.2V) for the M.2 cards. The SIM7100 for example requires at least 3.4V!