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Ayke van Laethem
9fdf0d657d
This is implemented in inline assembly using machine.CPUFrequency() to
know how long a single CPU cycle takes. As long as it is called with a
constant duration, it should be fully inlined and all values can be
const-propagated resulting in very tight inline assembly.
For example, when I convert i2csoft to use this delay function, the
entire delay function compiles to something like this:
8784: movs r6, #100
8786: mov r0, r6
8788: nop
878a: nop
878c: nop
878e: nop
8790: nop
8792: subs r0, #1
8794: bne 0x8788
That means that all the math to calculate the number of cycles is
entirely optimized away (in this case, to 100 loops).
I ran the example on a few boards to see how well it works:
| board | 100ms wait | CPU core
|-----------------------|------------|------
| microbit | 121.6ms | Cortex-M0 so it has 12% overhead
| circuitplay-express | 100.1ms | Cortex-M0+ so it is cycle accurate
| pico | 100.2ms | Cortex-M0+
| pyportal | 100.3ms | Cortex-M4
| circuitplay-bluefruit | 125.8ms | Cortex-M4
| esp8266 | 125.1ms |
This shows that there is some loop overhead because of conservative
estimates, but note that even though there may be a 25% overhead, the
actual overhead per `delay.Sleep()` call is very small. It should be
good enough for software I2C at least, and can potentially be improved
in the future.
TinyGo Drivers
This package provides a collection of hardware drivers for devices such as sensors and displays that can be used together with TinyGo.
Installing
go get tinygo.org/x/drivers
How to use
Here is an example in TinyGo that uses the BMP180 digital barometer:
package main
import (
"time"
"machine"
"tinygo.org/x/drivers/bmp180"
)
func main() {
machine.I2C0.Configure(machine.I2CConfig{})
sensor := bmp180.New(machine.I2C0)
sensor.Configure()
connected := sensor.Connected()
if !connected {
println("BMP180 not detected")
return
}
println("BMP180 detected")
for {
temp, _ := sensor.ReadTemperature()
println("Temperature:", float32(temp)/1000, "°C")
pressure, _ := sensor.ReadPressure()
println("Pressure", float32(pressure)/100000, "hPa")
time.Sleep(2 * time.Second)
}
}
Supported devices
There are currently 94 devices supported. For the complete list, please see: https://tinygo.org/docs/reference/devices/
Contributing
Your contributions are welcome!
Please take a look at our CONTRIBUTING.md document for details.
License
This project is licensed under the BSD 3-clause license, just like the Go project itself.