cc55ee6314
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com> Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
67 lines
2.1 KiB
Markdown
67 lines
2.1 KiB
Markdown
GrovePi Shield {#grovepi}
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=============================
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Mraa can use a GrovePi shield as a subplatform. This means one can utilize the
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shield IO as well as the IO on the carrier board. The GrovePi shield is meant
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for RPi boards and compatibles such as UP and UP2. It provides convenient GrovePi
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style connectors that can be used with various Grove sensors.
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Communication with the shield is achieved over I2C using a custom firmware. It
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provides access to extra GPIO, AIO and PWM pins.
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### Using the subplatform API ###
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Using the subplatform API is relatively simple, simply add '512', the platform
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offset, to any IO calls.
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Example:
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* D3 becomes GPIO 512 + 3 = 515
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* A2 becomes pin 512 + 2 = 514
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Keep in mind that the I2C ports on the GrovePi shield are merely a level shifted
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extension of the carrier board's I2C bus, hence I2C sensors do not require an
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offset.
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The API works from UPM or mraa in any of the supported languages and is compiled
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with mraa by default. Multiple subplatforms are not yet supported.
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### Pinout ###
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For a complete diagram of the pins available on these shields please refer to
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the hardware section of the [GrovePi Github repository](https://github.com/DexterInd/GrovePi).
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### Simple code example ###
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This piece of code fades an LED connected to D3 based on the position of a
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rotary potentiometer on A2:
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```c
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#include <stdbool.h>
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#include "mraa.h"
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void main (int argc, char** argv)
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{
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mraa_add_subplatform(MRAA_GROVEPI, "0");
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mraa_aio_context aio = mraa_aio_init(514);
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mraa_pwm_context pwm = mraa_pwm_init(515);
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while(true) {
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mraa_pwm_write(pwm, mraa_aio_read(aio)/1023.0);
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usleep(50000);
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}
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}
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```
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Note that the I2C bus number needs to be passed in as a string to
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`mraa_add_subplatform`.
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### Limitations & features to be added ###
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Currently there is no support for ISRs or the option to query the shield's
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firmware version, but these features may be added at a later point.
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Theoretically GrovePi Zero shields are compatible too, however they were not
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tested. Obviously, only a subset of the IO pins can be used due to the reduced
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footprint of this shield.
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