LattePanda Mu Free Trial Event
The application for the free trial event for the LattePanda Mu was approved on May 9th. I may receive the development hardware again. Once again, I am eternally grateful for this opportunity.
This means the pressure is now on again like it was in 2024 and this time I must not make the same mistakes. Fortunately, I was able to use a lot of the work I already did during 2024, especially the USB Type-C PD controller. I am not letting anything get in the way this time.
Codename and Branding
The codename for MediaCow Touch 2 Lite will remain to be "Curitiba", even after what happened a couple weeks ago. Mostly becuase I couldn't find a good replacement.
I started to use the aesthetics I had for MediaCow Touch 2 for the entire website on May 7.
Current Progress
I have finalized the symbol for the BQ25723 IC, fixed some of the Infineon MOSFET footprints and went through the process of drawing what is required for the battery management IC.
Battery Management
The Typical Application circuit for the BQ25723 shows seven 10uF capacitors in parallel between VSYS and the battery MOSFET with a similar configuration of six 10uF capacitors after the VBUS pin. It seems a bit excessive but I decided to keep it in after seeing that it is actually like this in a 3D model of an example application.
PROCHOT
The PROCHOT pin was kind of interesting to figure out. The BQ25723 example shows a 50 ohm pull-up resistor between PROCHOT and a 1.05v reference voltage. Since the reference voltage from the CPU cannot be used, an TCR3UF105A LDO regulator was used for this.
I still do not fully understand what PROCHOT does but it seems important to connect to the CPU.
VSYS Switch
The VSYS switch, the Infineon BTS7006-1EPP has historically been a challenge to figure out, specifically the IS pin that is used to read current and voltage through an analog signal. This seems Infineon-specific and I have not been able to find much information about it. It has actually lead to me trying to find one of these ICs in a vehicle at a junkyard though it is quite recent, being from 2018; most vehicles I find are from 2014 and older and with anything newer there, none of the computer-related parts survived or have not been removed. The datasheet also got a new revision on July 29, 2024, this being after I started development with this IC. Some things changed that I had to take into consideration though this was mostly with the IS pin.
For MediaCow Touch 2 Lite "Curitiba", the IS pin would be unused. I spent an unecessary amount of time trying to figure out how to connect the IS pin to the embedded controller where it is really not needed for this application, especially since the only thing being powered from it is the LattePanda Mu.
Audio
I was hesitant on including an audio CODEC on MediaCow Touch 2 Lite due to the challenges with analog audio but since MediaCow was originally an audio-oriented device, I decided to include one. This time I am using the Tempo 92HD95 CODEC since it uses the HD Audio interface that is available on the LattePanda Mu.