Power Monitor firmware for Chart Plotter Hat

Firmware for ATmega328P that monitors a push button to turn on/off a switching power supply. Supplies a shutdown signal to another MCU so that it can shutdown cleanly before the power supply is switched off.

Also implements ADC measurements in response to SPI requests.

Intended for use with Raspberry PI boat computer project. The corresponding hardware design is at:

Raspberry Pi scripts

The script shutdown_monitor.py is used to control and monitor the GPIO pins on the Raspberry Pi to work in concert with this firmware. This script is copied to /usr/bin. A systemd service file is shutdown_monitor.service and is copied to /lib/systemd/service.

Enabling and starting the service using systemd

systemctl enable shutdown_monitor.service
systemctl start shutdown_monitor.service

To disable the service from starting at boot

systemctl disable shutdown_monitor.service

Code

Diagram made using gaphor

Build instructions

Install Rust nightly.

rustup toolchain install nightly-2021-01-07

Then run:

cargo +nightly-2021-01-07 build --release

The final ELF executable file will then be available at target/avr-atmega328p/release/power-monitor-rust.elf.

ATMega328P fuse settings

The fuses are changed from the default and need to be updated

avrdude -p atmega328p -c <your programmer here> -U lfuse:w:0xc2:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m

Firmware Load

The compiled firmware (power-monitor-rust.hex) can be programmed into the hardware using

avrdude -p atmega328p -c <your programmer here> -U flash:w:power-monitor-rust.hex

To create the hex file, use avr-objcopy

avr-objcopy -O ihex target/avr-atmega328p/release/power-monitor-rust.elf power-monitor-rust.hex

This can also be done with the makefile target 'program', or make program

Chart Plotter Hat Hardware Changes

• Rev B

• LED1 attached to PB0

• LED removed from SHUTDOWN

• SHUTDOWN added pulldown

• MCU_RUNNING moved from PD3 to PB1

• MCU_RUNNING added pulldown

• LC circuit added to AVCC

• Optional 12V ADC measurement to ADC7

• Rev A (original)

PIN LAYOUT

                 [proto-board]
                ATmega328P-28P3            
            +--------------------+         
            |                    |         
      RESET-|1  PC6        PC5 29|-ADC5    
         RX-|2  PD0        PC4 27|-ADC4    
         TX-|3  PD1        PC3 26|-ADC3    
     BUTTON-|4  PD2        PC2 25|-ADC2    
       LED5-|5  PD3        PC1 24|-ADC1    
     ENABLE-|6  PD4        PC0 23|-ADC0    
        VCC-|7                 22|-GND     
        GND-|8                 21|-AREF    
   SHUTDOWN-|9  PB6            20|-AVCC    
     EEPROM-|10 PB7        PB5 19|-SCK     
       LED4-|11 PD5        PB4 18|-MISO    
       LED3-|12 PD6        PB3 17|-MOSI    
       LED2-|13 PD7        PB2 16|-CS
       LED1-|14 PB0        PB1 15|-MCU_RUNNING
            |                    |         
            +--------------------+         
            
                   ATmega328P-32A
            +--------------------------+        
            |                          |        
        3.3-|4  VCC              PB0 12|-LED1   
        3.3-|18 AVCC             PB1 13|-MCU_RUNNING
   CAP->GND-|20 AREF             PB2 14|-CS
        GND-|3  GND              PB3 15|-MOSI   
            |                    PB4 16|-MISO   
         A6-|19 ADC6             PB5 17|-SCK    
         A7-|22 ADC7             PB6  7|-SHUTDOWN
            |                    PB7  8|-EEPROM 
           -|30 PD0                    |        
           -|31 PD1              PC0 23|-A0     
     BUTTON-|32 PD2              PC1 24|-A1     
           -|1  PD3              PC2 25|-A2     
         EN-|2  PD4              PC3 26|-A3     
           -|9  PD5              PC4 27|-A4     
           -|10 PD6              PC5 28|-A5     
           -|11 PD7              PC6 29|-RESET  
            |                          |        
            +--------------------------+        

License

power-monitor-rust is licensed under the GNU General Public License v3.0 or later. See LICENSE for more info.