Binary executables can be compiled from gpioASM for tasks like power a motor until an endstop is reached, toggle an LED with a button press, turn a stepper motor until a hall sensor is triggered and many more.
Here are the available instructions:
| command | opcode | arguments |
|---|---|---|
write_digital |
0b0000---- |
digital bits |
write_analog_channel_0 |
0b00010000 |
uint16_t |
write_analog_channel_1 |
0b00010001 |
uint16_t |
write_analog_channel_2 |
0b00010010 |
uint16_t |
write_analog_channel_3 |
0b00010011 |
uint16_t |
sleep_ms |
0b00100000 |
varint |
sleep_match_all |
0b0011---- |
digital bits |
sleep_match_any |
0b0100---- |
digital bits |
sleep_match_all_timeout |
0b0101---- |
digital bits |
sleep_match_any_timeout |
0b0110---- |
digital bits |
jump |
0b01110000 |
varint |
check_bytecode_version |
0b10000000 |
varint |
jump_match_all |
0b1001---- |
varint, digital bits |
jump_match_any |
0b1010---- |
varint, digital bits |
jump_count |
0b10110000 |
varint, varint |
exit |
0b11000000 |
If an opcode contains dashes (----), those bits are filled with the size of the argument in bytes.
write_digital 01010 for example contains 5 pins, and since 2 bits are needed for each pin, this argument requires 2 bytes. The resulting opcode will be 0b00000010.
Digital bits represent logical states of digital GPIO pins. Every digital pin can be in one of four states:
| state bits | state description |
|---|---|
0b00 |
pin is LOW |
0b01 |
pin is HIGH |
0b10 |
pin is high-impedance |
0b11 |
pin is not available or ignored |
Pin states are represented via bytes.
Every byte can house up to four pin states, unconfigured pin bits are set to 0b11.
For example, five pins, states [HIGH, LOW, LOW, LOW, HIGH] are represented by two bytes, and look like this:
0b01000000 01111111
The amount of bytes to send depends on the amount of configured digital output pins.
If the chip boots with 6 digital output pins configured, it always expects a digital payload sized 2 bytes (CEIL(pin_count / 4)).
Varints are encoded integers that grow bytewise in size with higher integer values. Best described here.
unsigned integers, range from 0 - 65535, encoded as 16-bit little-endian.
Every command is encoded as its opcode and the arguments. No length or padding is encoded along.
write_digital 1001 becomes 0b00000000 01000001.
write_analog_channel_1 1000 becomes 0b00000000 00000011 11101000.
label start
write_digital 1
sleep_ms 100
write_digital 0
sleep_ms 100
jump start
becomes
wr.-dig. pin#0 1 sleep 100ms wr.-dit. pin#0 0 sleep 100ms jump addr 0
0b00000001 01111111 00100000 01100100 00000001 00111111 00100000 01100100 01000000 00000000