Mux_out connected to AIN7 or AIN6

[jge14]

Hi,
I’m trying to monitor battery voltage through AIN7 but the voltage remains constant for this channel. However, when I monitor AIN6 it’s consistent with the battery status, i.e. when the battery is being charged the value on AIN6 increases and when the board is running on battery, AIN6 decreases with time. I would like to confirm if AIN7 is connected to MUX_OUT or instead it’s AIN6 the one connected.

Thanks

Best regards,
Jose

• This topic was modified 3 years, 3 months ago by jge14.

[Eshtaartha Basu]

Hello jge14,

Thank you for bringing this to our notice. MUX_OUT is connected to AIN7 in hardware but there seems to be a pin muxing bug in software. Please see signal to ball mapping here for the bug – https://github.com/octavosystems/OSD335x-Device-Tree/blob/master/OSD335x_RED.pinmux

We will fix this bug soon and update OSD3358-SM-RED DT files to reflect the same. Thanks.

UPDATE: We verified the pinmux on the backend and IT IS CORRECT. The OSD335x-SM uses AM335x ZCZ package. Hence, the .pinmux file corresponds to pin mapping between signal names and balls numbers of AM335x ZCZ package.

By default MUX_OUT will be in High-Z. Make sure you’ve configured the PMIC registers properly to have the right input on AIN7. Which development board are you using?

• This reply was modified 3 years, 3 months ago by Eshtaartha Basu.

[jge14]

Hello Eshtaartha,
Thanks for your answer. I’m actually using BeagleBone Black-Wireless and I just realized that one uses OSD3358-BAS instead of OSD3358-SM. Then, should I post this in other forum or the solution is similar? Because I just looked on the schematic of that one a it shows that MUX_OUT is not connected to any ADC.

Thanks

Best regards,
Jose

[Eshtaartha Basu]

Hello jge14,

Since the question is posted under OSD335x-SM, I initially assumed you’re talking about OSD3358-SM-RED development board.

BeagleBone Black-Wireless uses OSD3358-BAS device.

On the OSD3358-BAS:

1. PMIC’s MUX_IN and MUX_OUT pins are not brought out of the SiP (not externally accessible for connections)
2. MUX_IN and MUX_OUT pins are not connected to anything (not connected to any ADC pins) within the SiP.

As seen on the BeagleBone Black-Wireless schematics, AIN7 is already being used to monitor output rail VDD_3V3B through resistor voltage divider (R21 and R22). This is why you’re seeing constant voltage. All other ADC pins including AIN6 are connected to BeagleBoard header P9.

Do you have anything on the P9 header(any BeagleBoard cape)? How are you charging the battery? Some external connection on P9 is probably making battery voltage appear on AIN6. Please check your connections.

[jge14]

Hello Eshtaartha,

Thanks for your answer. I verified with another BBB-W and the behavior is not shown there.
I’m charging the battery with the 10k resistance between TP4(BAT_TEMP) and TP5(GDN) and connecting TP3(BAT_VOLT) to TP2(VIN_BAT). (Page 10 of OSD3358 Application Guide Rev.5 4/25/2017)
Then, to monitor the battery I’m going to connect TP3 to one of the ADC. Do you have any suggestion besides guaranteeing that the voltage is below 1.8V?

Thanks!

Best regards,
Jose

[Eshtaartha Basu]

Hello jge14,

Sounds good. The connections seem correct.
We recommend this app note on battery usage with OSD335x – https://octavosystems.com/app_notes/am335x-battery-applications-with-osd335x-sip/.

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