I’ve been working with a USB cabled connection from the start so I can view output in a terminal but I’m developing a battery powered application. I am now starting to work off a 1200mAh Li-Ion battery that I bought for development. The 500mAh one seemed to discharge quickly so that’s why I increased capacity.
With the battery fully charged I run for about an hour when I start noticing my app startup banner popping into view and then quickly disappearing as normal program output starts. It was doing this before with the smaller battery that comes with the GO but now it was happening with a much larger battery.
To investigate I hooked up a Rigol DP832 power supply and programmed it to output 5V initially with the intention of reducing the voltage to see when the module started misbehaving. I connected the power supply leads to the +5V and GND pins on my the Dock (I have several of these boards) and I connected my Picoscope 5443D MSO probes to the Dock pins: 5V (A-Blue), 3.3V (B-Red), 1.8V (C-Green) and RST (D-Yellow/Brown). With that setup I stepped the voltage down in 0.01V increments and everythig was fine until until I got to about 3.6V at which point the device started resetting. The following image demonstrates this behavior.
I am seeing this with both Dock boards but the 2nd board survives until ~3.4V. I have more Dock’s I can test as well as the GO board that I also have. The GO trips at 3.64V. RST is generated under the can on the M1 module so this must be happening internally to the module and not from something on the PCB.
A system that is designed to run on a 3.7V battery which resets when the supply voltage is only 3.65V isn’t very helpful. It really should be fine down to 3.3V as that voltage will be available from most 3.7V Li-Ion batteries up until it is nearly depleted, at which point the voltage crashes. Typical curves…
Can someone else check my findings to confirm what I am seeing. I would certainly like someone from Sipeed to look into this and provide comment.
Thanks for reading.