BoSL Board v0.5
2023 September 28
The BoSL board rev 0.5.0 arrived and its time to test how it works. Lets jump into it!
Straight out of the packet:
- Plugging in a battery the idle current 840 µA.
- Touching a screw driver to the F1 TEST pad lights up the test LED.
- When the WDT_EN jumper is closed the current jumps up to ~10 mA. This seems appropriate, if it enables the voltage on VPP.
From now on WDT_EN will be closed
- Voltage is good on 3V3 and VBAT. Measured (3.370V and 3.941V respectively).
- The bootloader could be programmed using the normal process of Arduino as ISP. Specifically I used the [[1]] board library and selected the ATmega640 board. I then used BOD: 2.7V, bootloader: yes UART0, clock: external 8MHz, EEPROM: EEPROM retain, compiler LTO: LTO disabled, pinout: AVR pinout.
- Idle current now 18 mA.
- I then plugged in the board via USB and it was recognised as a serial port.
- Programs could be uploaded via USB now, the serial monitor analogue read, and the RX,TX, LED, and USB, LEDs work.
- I could get a response form the SIM7000 when I made the following changes to the BoSLpass script.
- Replaced simCom soft serial object with Serial1
- set PWRKEY 38, DTR 44, and defined SIM_BUF_EN 25
- Pulled SIM_BUF_EN HIGH to turn on the voltage level converter.
- When I did this I could talk to the sim and recognise the simcard, but not register to the network. I suspect this is due to no Telstra reception here:
23:14:41.086 -> sending: AT+COPS=? 23:14:41.130 -> 23:37:12.814 -> 23:37:12.814 -> +COPS: (1,"vodafone AU","voda AU","50503",9),(1,"Optus AU","Optus","50502",9),,(0,1,2,3,4)
Firmware updates:
- Now that we have the more pins it would we wise to wrap each call which writes to the serial of the SIM7000 to first check CTS and RTS and see that we are allowed to send.
Errors:
- WDT_EN is not the correct name for the jumper as the WDT is disabled when closed. It should be not WDT_EN
- Add silkscreen for female pin headers
- Fix the pinout for U8, the MCP1700T-3302E which currently has the VPP and 3V3 swapped.
23 November 26
Today I am testing the idle current draw of the BoSL board. First is to test the idle current when Q1 shuts off +BATT from VPP. All tests here are with WDT_EN open.
I swapped the orientation of U8 (MCP1700T-3302E) as it was incorrect. Doing this resulted in the idle current from 1.1 mA to 0.87 mA.
I do not notice any "floating rails" however if WDT_EN is enabled and then disabled it will take a long time for the VPP rail to return to 0V as the connected capacitors need time to discharge.
Removing the Zener diode for reverse current protection (D10) results in a current of 0.64 mA or a drop of approximately 200 μA.
