Review on 📶 HiLetgo SIM800L GPRS GSM Quad-Band Breakout Module with SIM Card Slot, Antenna, and Input Voltage Range of 3.7~4.2V by Pete Norris

I bought five of these in two separate orders. The first two that came did not recognize the SIM card. I was able to determine that this was due to the I/O line on the SIM not being raised high and therefore not reading the SIM's response correctly (because the IO line would remain logically low) . See the attached image of a working SIM ATR reply (left) and erratic I/O behavior on two of these modules (right). Please note that these tests were run back-to-back using the same SIM card with the same results. The second order I received worked fully and I can tell its shape differs from the kit (and probably many parts/assemblies) as the parts included in the kit are slightly different (2 sets of 7 pins vs 2 sets of 6 pins). pin connectors). Three working ones work fine, but with a 40% chance of failure, their cost increases significantly. You can buy the same boards from other vendors on Amazon, I'm not sure if their reliability is better or worse but I would suggest giving it a try. Alternative.