So I purchased this bare sim800l module which only has pins and an LED and some resistors which means it has no voltage regulator or anything. For the past month I was able to use it with 2 different sim cards from different companies. I was building a software for it to work with stm32 MCUs. Yesterday I finally managed to send MQTT messages to hivemq so I let it stay on and send msges for some hours to make sure my software does not freeze. Then I decided to change the program a bit and after I flashed the program, the module stopped detecting my Sim card. Now it only blinks rapidly as if looking for network and my software reports connection errors.
I hooked it up to my PC, it responds to my AT commands but when I enter At + CIEE2 and then AT+CPIN? it responds with Sim not inserted. It does so with both Sim cards(both work OK on phone). The thing is I did not move the Sim card nor did I drop the module or do anything to physically move the Sim so the fact that it suddenly stopped recognizing them is strange and I tried both Sim cards which used to work with the same result.
I was using a 1600mAh LIPO battery the whole time to power the module(it is fully charged now) but I was connecting it to my MCU directly(3.3 volts) everyone says it is 3.3 v tolerant but here Ravi says 2.8 max? Maybe I fried something in there? I do not have a logic analyzer nor do I have a soldering station for SMD parts so I have ordered a new module, I just wanna know what I did wrong so as to not fry the new module.
Any kind of tips or suggestions would be appreciated thank you