BoSL Board v0.3

BOSL BOARD - THE ULTRA LOW POWERED IOT LOGGING DEVICE

This little beauty costs less than an Arduino and Sim5320a put together, yet it comes already assembled, runs on 4v, is ultra low power consuming (we removed all the overheads of the off the shelf arduinos) and can send data via the CAT-M1 or NB-IoT networks! We estimate that these things can log each minute for over 12months!

SIM7000 SIM CARD COMMUNITCATION ISSUE

2019/11/21:

There has been an issue where some of our boards aren't recognising the SIM cards, and so can't upload any data. To detect is if the issue is present the following AT command sequence can be sent.

GOOD RESPONSE

Command	Response
AT+CFUN=0
	+CPIN: NOT READY
	OK
AT+CFUN=1
	OK
	+CPIN = READY
	SIM READY

BAD RESPONSE

Command	Response
AT+CFUN=0
	+CPIN: NOT READY
	OK
AT+CFUN=1
	OK
	+CPIN: NOT INSERTED

We did some probing around with an oscilloscope to see if there were any electrical differences between the good and bad boards. Both had identical measured crystal frequencies of 7.9 - 8.1 MHz and SIM7000 - ATmega382p baud rates of about 9540.

The one difference which was found was in the signals issued from the SIM 7000 to the SIM card on pins SIM_VDD, SIM_RST, SIM_CLK, and SIM_DATA. They are quite different. Notably the bad boards only power the SIM VDD line for 3 pulses of 24 ms long whereas the working boards good boards keep this line high. The measurements are taken after the AT+CFUN=1 command is issued in the above test sequence.

In doing some reading on the issue it seems to have been encountered before, with the conclusion that it likely a soldering issue, possible inside the SIM7000 modual, thus leaving little course for it to be able to repaired.

for boards with a SIM inserted

PIN	Good Board	Bad Board
SIM_VDD	GOOD VDD SIM	BAD VDD SIM
SIM_RST	GOOD RST SIM	BAD RST SIM
SIM_CLK	GOOD CLK SIM	BAD CLK SIM
SIM_DATA	GOOD DATA SIM	No Reading

for boards without a SIM inserted

PIN	Good Board	Bad Board
SIM_VDD	GOOD VDD NSIM	BAD VDD NSIM
SIM_RST	GOOD RST NSIM	BAD RST NSIM
SIM_CLK	GOOD CLK NSIM	BAD CLK NSIM
SIM_DATA	GOOD DATA NSIM	No Reading