Artemis ATP low power consumption

Development Boards Artemis
1

Hello guys.

I’d like to run some power consumption experiments on an Artemis ATP board. I have a custom-made shield and I want to measure its added consumption to the main board. What I try is to cut the MEAS jumper and feed the MCU-part (VDD line) of the board with 3.3V. I also injected an ammeter into this power supply circuit. In deep sleep mode + DMA ADC transfers are running, the value is around 6mA, which is an extra high value. Then, I also plug in the USB cable and the consumption drops down to 1mA, which is acceptable. I cannot figure out what’s going on… Its like the VDD somehow feeds the rest of the (unused parts of the) board but not through the MEAS connector? I can experience the same, inverted effect, too: when I remove the jumper from the already cut MEAS pins, the MCU keeps running. It’s getting some sort of a “phantom” power from elsewhere?

Thanks.

Gyorgy

2

Hi Gyorgy.

Looking at the schematic, it looks like the CH340 IC might be phantom powering the Artemis module via RX and TX when you’re plugged into USB. That would explain the current drop when you plug USB in.

Also, if you have anything connected to IOREF or the 3.3V pin on the board, those get added to what you measure across MEAS.

3

Hi Chris

Thank you. You were right, those pins caused the issue. This thread can be closed.

To solve the power consumption problem, I changed the mentioned TX and RX default pins to inputs, which I did by adding the following lines:

am_hal_gpio_pinconfig(48, g_AM_HAL_GPIO_INPUT);

am_hal_gpio_pinconfig(49, g_AM_HAL_GPIO_INPUT);

The pwr cons. dropped from 5mA to 0,9mA. As the Artemis boards include an ultra-low-power MCU, I believe that the folks out there who try to use this board are interested in low-power applications. It might be a good idea to implement an init_low_power_NO_UART() or similar function that disables the phantom powering lines by default.

Thanks again!