AXEL ULite adapter
AXEL ULite adapter is a board that DAVE Embedded Systems has made available to make initial development on AXEL ULite-based systems easier.
The following sections illustrate in more detail what it integrates and how to use it.
In principle it can be used with any carrier board designed to host 3.3V-powered AXEL ULite SOM. These SOMs have the ordering code in one of the following forms:
DA p l r n c 0 t s
DA p l r n c 1 t s
DA p l r n c 3 t s.
AXEL ULite adapter has to be interposed between the carrier board and AXEL ULite SOM as shown by the following picture.
Once hardware boards have been assembled,
BOOT_CFG signals have to be configured in order to select the desired boot options.
As described here, GPIO ovverride mode is extremely helpful when it comes to select different boot configuration options. AXEL ULite adapter provides a bank of switches that allows to change both
LCD1_DATAx signals affecting boot configurations. When the switch is in ON position, "0" logic level is selected.
The following table lists all the switches in detail.
|Switch reference||iMX6UL signal name||Correspondent eFUSE|
Low-power RTC example
From the point of view of power status, AXEL ULite SOM can operate in different modes. When operating in SNVS mode, power comnsumption may be relatively high if:
- iMX6UL RTC is the only part that actually needs to be powered
- SNVS domain is powered by a limited-capacity energy storage device, such as coin cell Lithium battery or supercap.
In this case it is suggested to consider the use of an external low-power RTC instead. AXEL ULite adapter integrates such an RTC (ST M41T83) that allows the user to compare this solution with respect to the one based on iMX6UL native RTC.
Please note that, when the system is powered off nad the extarnal RTC is used, SNVS domain is not powered at all because rechargeable coin cell is connected to M41T83 only.
Power consumption measurement circuit
This circuit is based on Texas Instruments INA226 and it is used to measure power consumption of AXEL ULite SOM. This device is accessible via I2C bus either by iMX6UL itself  or by an external host connected to test points TP3 and TP4.
 Clearly this is not possible for all of the iMX6UL operating modes.
I/O voltage sequencing and monitoring
AXEL ULite SOM is powered by VIN_3V3 that, in turn, originates at carrier board level. VIN_3V3 is connected to the net VIN_SOM through a shunt resistor (R12) that is used by power measurement circuit.
The rest of the circuitry is powered by 3.3V rail that is turned on via U70 switch. This switch - enabled by the SOM_PGOOD signal - is used to implement proper power up sequence, as described here.
A tiny microcontroller (U68) is used to implement a voltage monitoring circuit to verify that the difference between native AXEL ULite I/O voltage (SOM_3V3_IO) and 3.3V does not exceed 300mV, as per design requirement. In case this condition is not met, the microcontroller triggers a full power up cycle via PMIC_PWRON.
- Schematics: TBD
- BOM: TBD
- Layout: TBD
- CAD Drawings: TBD