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Published On: June, 29, 2020 By: Justin Berry | Updated: December 1, 2020 by Cathleen Wicks
This application note describes how to reprogram the non-volatile memory (NVM) within the Power Management Integrated Circuit (PMIC), the STPMIC1, for OSD32MP15x Devices. The PMIC stores the initial configuration of the output power rails, startup conditions, etc. in NVM that is loaded during the power-up sequence. By default, the NVM in the OSD32MP15x is set to the values for the STPMIC1A configuration. However, a customer may want to modify this initial configuration in their application or design. For example, by default, the threshold voltage required to turn on the PMIC, VINOK_THRES, is 3.5 Volts. To power the OSD32MP15x using a 3.3 Volt regulator, the VINOK_THRES in NVM must be modified to a lower value. This application will walk you through an example of the 3 basic steps:
The non-volatile memory (NVM) is described in detail in various sections within the STPMIC datasheet. Some important sections include:
For this application note, we have provided two Python scripts:
Both scripts run using Python version 3, i.e. python3, and are open source so that they can be easily customized for a given application. Details about script are in comments near the top and throughout the file.
Typically these scripts are run during the provisioning or test process in the manufacturing flow of the product, however they can be run at anytime if the NVM values need to be modified.
Below is a picture of the PMIC state machine. By making sure the device is adequately powered, you move from top to bottom along the right side of the state machine. Once the device is in POWER_ON/MAINMODE, you can reprogram the PMIC. Any new power up conditions will come into effect the next time the device is booted up.
In order for the NVM in the PMIC to be programmed the PMIC MUST BE IN THE POWER_ON/MAIN MODE state.
Since the PMIC needs to be fully powered on to be reprogrammed, the STM32MP15x processor inside the OSD32MP15x will also be powered and can be used to reprogram the NVM of the PMIC. The above scripts were designed to run on the STM32MP15x processor within the OSD32MP15x system-in-package device. However, they may be run on an external device connected to the I2C4 bus (i.e. the PZ4/PMIC_SCL and PZ5/PMIC_SDA pins) of the device.
This section will discuss the hardware and software required to set up and run the PMIC reprogramming software. In this application note, we will run the reprogramming scripts on the STM32MP1 processor inside the SiP, specifically we will use the OSD32MP1-BRK as our platform.
The hardware required to program the NVM in the PMIC is:
In this example, no external components are needed to program the PMIC since the STM32MP15x processor is connected via I2C to the STPMIC1 within the OSD32MP15x.
If you choose to use an external device, you will need to make sure it is powered and connected to the PZ4/PMIC_SCL and PZ5/PMIC_SDA pins via I2C.
The software required for this application note is:
No additional software components are needed.
Note: The Debian Linux image from Octavo Systems already contains the necessary python installation to run the provided software.
This section details the procedures to setup the OSDMP1-BRK and to reprogram the PMIC NVM.
The goal of this section is to get power to the device and make the necessary python scripts available for use on device. Each system is different so how you do this will depend greatly on your setup.
The following procedure describes the steps to load the Scripts on the OSD32MP1-BRK which was set up following the steps in the Getting Started Guide:
The following procedure describes how to use the provided software to write new values to the PMIC NVM:
debian@localhost:~$ sudo su
[sudo] password for debian:
root@localhost:/home/debian#
root@localhost:/home/debian# python3 pmic_read_reg.py
The script is configured by default to run on the default Octavo Systems Debian Linux image for the OSD32MP1-BRK. In the default configuration the STPMIC1 is connected to the STM32MP15x on I2C4. Therefore, the script by default will use the I2C bus “3” (I2C buses are numbered 0,1,2, 3 in OS and alias I2C1, I2C2, I2C5, I2C4 ports) for communication. If your device tree configuration is different from the default Debian Image for the OSD32MP1-BRK board, you may need to check which I2C port the PMIC SCL and SDA, i.e. pin PZ4 and PZ5 on the SiP, are assigned. Below is an example error message if the I2C bus is not set properly.
To fix this, you can use the command argument “–-i2c=” to change the I2C bus number used to communicate to the PMIC. For example:
root@localhost:/home/debian# python3 pmic_read_reg.py --i2c=”3”
If successful, the script will print out something like this:
2. After validating the connection to the STPMIC1, you can now modify this PMIC NVM with the following command:
root@localhost:/home/debian# python3 pmic_reprogram_nvm.py
If you get the following error, your i2c bus number may be the problem:
The i2c bus number should be the same as value from Step 1. To fix the error, you can use the command argument “–-i2c=” to change the I2C bus number used to communicate to the PMIC. For example:
root@localhost:/home/debian# python3 pmic_reprogram_nvm.py --i2c=”3”
By default, the script sets VINOK_THRESH to 3.5V (i.e. the STPMIC1A configuration). If you wish to set it to another value, you can use the command argument “–vin_ok=” which can have a value of [“3.1”, “3.3”, “3.5”, or “4.0”} Volts. For example:
root@localhost:/home/debian# python3 pmic_reprogram_nvm.py --i2c=”3” --vin_ok=”3.3”
3. When the value is written, you will see three tables and a message saying “PASSED”. For example:
With this, the NVM in the PMIC has been successfully reprogrammed.
This application note shows how to use the provided software to re-program the non-volatile memory (NVM) within the power management integrated circuit (PMIC) for the OSD32MP15x family of devices. For any questions or comments, please post on our forums.
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| Revision Number | Revision Date | Changes | Author |
|---|---|---|---|
| 1 | 6/26/2020 | Initial Release | Justin Berry |
There has been multiple revisions to the OSDZU3-REF and some of the documentation is for specific revisions.
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