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I connected a SIM7605CE module to the PC (Image shown below).

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I downloaded and installed all the necessary firmware for the device. I connected the device to a 5V DC power supply and connected it to the PC using a USB connection. The COM ports are as shown below.

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When I try to connect to COM9 and open up putty to try and communicate with this device using ATI commands, I can't type anything. The only thing that goes through is 'A' or 'a'. Nothing else. What could be causing this issue? Strange thing is, it actually worked some time ago. I was able to communicate using AT commands. (The usual 'AT', 'ATI', etc.). Baud rate is 9600.

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The current situation looks something like this.

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C Vith
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  • does it say anything when you turn it on or reset it? – BeB00 May 17 '21 at 04:13
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    Not much resonates with me. But a few: (1) I assume you understand about putty and echo on/off mode and that the echo is off. (2) If so, it's possible that the bit rates *aren't matched* (but you think they are) and that ***some*** of the character patterns can trick the unit into thinking they aren't an error. For example, "A" is 1000001 and 'a' is 1100001. In some cases the paired 11's aren't all that different from a single 1. Shouldn't happen, but might. The USB virtual COM port cannot have that problem, itself. But if a USB MCU is tied to a 2nd not-USB MCU, then it's possible. – jonk May 17 '21 at 05:33
  • That said, have you tried a different computer? It would help eliminate a lot of possible problems if you did all this on a 2nd computer to see if the behavior is the same, or not. – jonk May 17 '21 at 05:34
  • @BeB00 it will sometimes say that the SIM card is not detected (which is correct, there is no SIM put into the module). But sometimes it will show nothing. Either way, I can't seem to type anything other than the letter 'A'... – C Vith May 17 '21 at 06:03
  • @jonk I will see if I can try it out on another computer. For the time being, I will see if there are any changes I can do with this PC. – C Vith May 17 '21 at 06:15
  • Once upon in the past, similar modems had a autobaudrate feature if you enabled it. To initialize, you had to output a sequence of 'A' and then module baudrate was set. – Marko Buršič May 17 '21 at 06:50

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