ATmega328p Serial Pulser

ATmega328p bare-metal firmware for precise pulse generation controlled via serial commands.

1. Wiring

• Pulse Output: PD3 (D3 in Arduino Nano)
• Status LED: (PB5 (D13 in Arduino Nano, which is the built-in LED)

2. Build & Flash

Compile with

make       

Flash with (Requires avrdude)

make flash 

3. Operation

The generator is controlled via serial interface. Commands must be sent at 9600 baud:

stty -F /dev/ttyUSB0 9600

Modes of operation

There are three

• Single Pulse (0)
• Multi-pulse burst (1)
• Continuous (2)

You can set one of these modes by sending an m command. For instance, to set the generator to continuous mode run

echo "m2\n" > /dev/ttyUSB0 

Commands

Command	Description	Parameter range
t	Trigger	-
m	Change operation mode	1 (Single pulse), 2 (Multi-pulse burst), 3 (Continuous)
d<param>	Pulse width (ms)	1 - 274873713
p<param>	Total period (ms)	d - 274873713
c<param>	Pulse Count (mode 1)	1 - 255
s	Stop	-

Pulse duration and period

This uses Timer1 to count both pulse duration and pulse period. The timer can count up to $2^{16} - 1 = 65535$ ticks, with each tick lasting $1024/16\ \text{MHz} = 64\ \mu\text{s}$. This gives a maximum single-segment duration of $65535 \times 64\ \mu\text{s} = 4.19424\ \text{s}$. For longer pulse duration/periods, we chain multiple overflows. The total time becomes $(N + 1) \times 4.19424\ \text{s}$, where $N$ is the maximum number of overflows. Since we are using uint16_t to store the required overflows, the theoretical maximum period is $274873713\ \text{ms} \approx 76.35\ \text{h}$.