Before the National-Day holiday, we sent out more than 150 sets of Iteaduino Plus, and they have been arriving at the customers. We are also having a colleague communicate with the customers and follow up with the feedback.
Seeing from the feedback received till now, there are two main problems with the hardware:
Some customers cannot boot directly into the system when powering up the board, and they need to manually press the power button on the core board to get it started or to re-plug the USB power cable to enter the system. During testing, we did not encounter such situation until we replace with a poor power supply and occasionally such phenomenon appeared. After examination, we found that it is because the instantaneous current is quite large while powering up, if the power supply performance is poor, there will be a low transient voltage, and AXP209 PMU chip will not get started as it takes there is an error on power, so you need to manually press the power button to get it booted.
To fix the power compatibility issues , we will add a large capacitor in power section on the new board. For guys who have received the boards, we recommend you to add a 470uF capacitor between pin 5V and pin GND to solve the problem.
Another problem is that when using reboot command to restart, sometimes it will get stucked and the system cannot be restarted. After inspection, we found that this was due to a mistake on the hardware design, RX line of UART 0 is connected directly to 5pin socket from the chip pin without protection processing. After the system is rebooted and enters countdown, if the RX pin of UART0 is interrupted, the system will enter uboot mode instead of entering ITEAD OS, which seems to be crashed .
Solution to this problem would be to pull up RX pin of UART0 via a 10K resistor, thus the system will not enter uboot when counting down after rebooting. UART0 pins are also broken out on both sides of the board, users who have received the board can connect it with a 5V power supply to solve this problem .
In addition, with regard to the battery holder at the bottom of Iteaduino Plus mainboard, some users asked which type of battery can be used, we are very sorry to say that current design of the mainboard does not support battery-powering. Although we reserved the cell interface , due to size of the board and other reasons, battery powering and charging functions were not realized at last.