AXEL ULite adapter

Info Box Applies to AXEL ULite

Introduction

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.

Installation

AXEL ULite adapter has to be interposed between the carrier board and AXEL ULite SOM as shown by the following picture.

TBD

Once hardware boards have been assembled, BOOT_MODE and BOOT_CFG signals have to be configured in order to select the desired boot options.

Boot configuration

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 BOOT_MODE and 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
S4.1	BOOT_MODE0	n/a
S4.2	BOOT_MODE1	n/a
S1.8	LCD1_DATA00	BOOT_CFG1[0]
S1.7	LCD1_DATA01	BOOT_CFG1[1]
S1.6	LCD1_DATA02	BOOT_CFG1[2]
S1.5	LCD1_DATA03	BOOT_CFG1[3]
S1.4	LCD1_DATA04	BOOT_CFG1[4]
S1.3	LCD1_DATA05	BOOT_CFG1[5]
S1.2	LCD1_DATA06	BOOT_CFG1[6]
S1.1	LCD1_DATA07	BOOT_CFG1[7]
S2.8	LCD1_DATA08	BOOT_CFG2[0]
S2.7	LCD1_DATA09	BOOT_CFG2[1]
S2.6	LCD1_DATA10	BOOT_CFG2[2]
S2.5	LCD1_DATA11	BOOT_CFG2[3]
S2.4	LCD1_DATA12	BOOT_CFG2[4]
S2.3	LCD1_DATA13	BOOT_CFG2[5]
S2.2	LCD1_DATA14	BOOT_CFG2[6]
S2.1	LCD1_DATA15	BOOT_CFG2[7]
S3.8	LCD1_DATA16	BOOT_CFG4[0]
S3.7	LCD1_DATA17	BOOT_CFG4[1]
S3.6	LCD1_DATA18	BOOT_CFG4[2]
S3.5	LCD1_DATA19	BOOT_CFG4[3]
S3.4	LCD1_DATA20	BOOT_CFG4[4]
S3.3	LCD1_DATA21	BOOT_CFG4[5]
S3.2	LCD1_DATA22	BOOT_CFG4[6]
S3.1	LCD1_DATA23	BOOT_CFG4[7]

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 [1] or by an external host connected to test points TP3 and TP4.

[1] 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.

Documentation

• Schematics: TBD
• BOM: TBD
• Layout: TBD
• CAD Drawings: TBD