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Read and translate AHT20 sensor readings

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This commit is contained in:
Leon Krieg
2024-09-03 22:42:10 +02:00
parent 83f6fa58a4
commit b9443f8cec
6 changed files with 225 additions and 196 deletions
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2
Makefile
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@@ -33,7 +33,7 @@ RMR := rm -rf
CPPFLAGS := -DF_CPU=$(FREQ) -I$(SRCDIR)
CFLAGS := -mmcu=$(MCU) -Os -std=c99 -Wall -Wextra -Werror
OCFLAGS := -j .text -j .data -O ihex
LDFLAGS := -mmcu=$(MCU)
LDFLAGS := -mmcu=$(MCU) -Wl,-u,vfprintf -lprintf_flt
LDLIBS :=
# ==============================================================================

45
docs/README
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@@ -1,49 +1,10 @@
## Serial Interface
Instead of polling for input we use an interrupt vector
to write data to a rx ring buffer when it's available.
We parse commands using a state machine so we can deal
with small chunks of characters at a time and spit out
the parsed command when the transmission has finished.
NOTE: System clock frequency should be a multiple of
1.8432MHz for perfect USART. This means we would need
an external crystal oscillator.
### Supported Commands
## Supported Commands
- RUN
- STOP
- TEMP <num>
- DEWP <num>
- TEMP <float>
- DEWP <float>
Decimal point for numbers is currently not supported.
Make sure you have disabled hardware flow control on
the client side.
### Web Interface Example
There is an example https and websocket server (written
in Python) which serves a simple Javascript shell that
controls your box. Its main purpose is to give you a
demonstration on how you can write a custom bridge or
interface.
Check out the directory "/opt/webgui" under the project
root. You may need to run the following command to load
optional submodules if you can't see the webgui folder:
$ git submodule update --init
First you need to generate a self signed certificate to
ensure SSL encryption. Run the following command in the
webgui root directory:
$ ./configure
To manually start the server you can use the Makefile
(but it's recommended to run the server automatically
as a daemon when the host machine starts):
$ make run

178
src/bus/twi.c
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@@ -16,6 +16,11 @@
// XXX: Handle interrupts in TWI_vect ISR? This may not
// actually be much better than the blocking approach
static void TWI_AHT20_Reset(void);
static bool TWI_AHT20_IsCalibrated(void);
static void TWI_AHT20_Calibrate(void);
static void TWI_AHT20_Trigger(void);
int TWI_Init(void)
{
// Set SCL bit rate to 400kHz
@@ -139,11 +144,6 @@ int TWI_SetChannel(int channel)
{
unsigned char crb;
// assert(channel >= 0 && channel <= 3);
// PCA9546 I2C Multiplexer
// =======================
Info("Switching I2C channel to %d...", channel);
// Excerpts taken from the PCA9546A datasheet:
@@ -187,3 +187,171 @@ int TWI_SetChannel(int channel)
return 0;
}
int TWI_AHT20_Init(void)
{
TWI_AHT20_Reset();
// Wait 40ms after power-on
Sleep(40);
Info("Initializing AHT20 sensor...");
if (!TWI_AHT20_IsCalibrated()) {
TWI_AHT20_Calibrate();
if (!TWI_AHT20_IsCalibrated()) {
Info("Error: Calibration failed.");
return -1;
}
}
return 0;
}
int TWI_AHT20_Read(float *temp, float *rhum)
{
unsigned char data[6], crc;
unsigned long hraw, traw;
TWI_AHT20_Trigger();
TWI_Start(0x38, 1);
TWI_Wait_ACK();
data[0] = TWI_Read_ACK();
data[1] = TWI_Read_ACK();
data[2] = TWI_Read_ACK();
data[3] = TWI_Read_ACK();
data[4] = TWI_Read_ACK();
data[5] = TWI_Read_ACK();
crc = TWI_Read_NACK();
TWI_Stop();
// After receiving six bytes, the next byte is the
// CRC check data, the user can read it as needed,
// if the receiving end needs CRC check, then send
// it after receiving the sixth byte ACK response,
// otherwise NACK is sent out, CRC initial value is
// 0xFF. The CRC8 check polynomial is:
// CRC[7:0]= 1 + (x^4) + (x^5) + (x^8)
// TODO: Implement CRC8 check
UNUSED(crc);
hraw = (unsigned long) data[1] << 12;
hraw |= (unsigned short) data[2] << 4;
hraw |= data[3] >> 4;
traw = (unsigned long) (data[3] & 0x0F) << 16;
traw |= (unsigned short) data[4] << 8;
traw |= data[5];
*rhum = (float) hraw / 1048576.0f * 100.0f;
*temp = (float) traw / 1048576.0f * 200.0f - 50.0f;
return 0;
}
static void TWI_AHT20_Reset(void)
{
// The command 0xBA is used to restart the sensor
// system without turning the power off and on
// again. After receiving this command, the sensor
// system begins to re-initialize and restore the
// default setting state. The time required for
// soft reset does not exceed 20 ms.
TWI_Start(0x38, 0);
TWI_Wait_ACK();
TWI_Write(0xBA);
TWI_Wait_ACK();
TWI_Stop();
Sleep(20);
}
static bool TWI_AHT20_IsCalibrated(void)
{
unsigned char status;
// Before reading the temperature and humidity
// values, first check whether the calibration
// enable bit Bit [3] of the status word is 1 (you
// can get a byte of status word by sending 0x71).
TWI_Start(0x38, 0);
TWI_Wait_ACK();
TWI_Write(0x71);
TWI_Wait_ACK();
TWI_Stop();
TWI_Start(0x38, 1);
TWI_Wait_ACK();
status = TWI_Read_NACK();
TWI_Stop();
// Note: The calibration status check only needs to
// be checked at power-on. No operation is required
// during the normal acquisition process.
return status & BIT(3);
}
static void TWI_AHT20_Calibrate(void)
{
// To calibrate you need to send 0xBE command (for
// initialization), this command parameter has two
// bytes, the first byte is 0x08, the second byte
// is 0x00, and then wait for 10ms.
TWI_Start(0x38, 0);
TWI_Wait_ACK();
TWI_Write(0xBE);
TWI_Wait_ACK();
TWI_Write(0x08);
TWI_Wait_ACK();
TWI_Write(0x00);
TWI_Wait_ACK();
TWI_Stop();
}
static void TWI_AHT20_Trigger(void)
{
unsigned char status;
// Send the 0xAC command directly (trigger
// measurement). The parameter of this command has
// two bytes, the first byte is 0x33 and the second
// byte is 0x00.
TWI_Start(0x38, 0);
TWI_Wait_ACK();
TWI_Write(0xAC);
TWI_Wait_ACK();
TWI_Write(0x33);
TWI_Wait_ACK();
TWI_Write(0x00);
TWI_Wait_ACK();
TWI_Stop();
// Wait for 80ms to wait for the measurement to be
// completed. If the read status word Bit [7] is 0,
// it indicates that the measurement is completed,
// and six bytes can be read in a row. Otherwise
// continue to wait.
TWI_Start(0x38, 1);
TWI_Wait_ACK();
do {
Sleep(80);
status = TWI_Read_ACK();
} while ((status & BIT(7)) == 1);
TWI_Stop();
}

3
src/bus/twi.h
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@@ -15,4 +15,7 @@ unsigned char TWI_Read_NACK(void);
int TWI_Wait_ACK(void);
int TWI_Stop(void);
int TWI_AHT20_Init(void);
int TWI_AHT20_Read(float *temp, float *rhum);
#endif // MAD_CORE_BUS_TWI_H

1
src/common.h
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@@ -2,6 +2,7 @@
#define MAD_CORE_COMMON_H
#include <stddef.h>
#include <stdint.h>
#include <stdarg.h>
#include <stdbool.h>

176
src/main.c
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@@ -6,137 +6,14 @@
#include <avr/interrupt.h>
short TWI_ReadAHT20(void)
{
unsigned char data, crc;
// TODO: Get readings from ADC ADS1115 over TWI.
// TODO: Implement optional sensor value check with CRC8.
// TODO: Either implement software PWM for the FAN03 timer
// (which will be quite complicated) or pick a chip with
// more than two 16-bit PWM outputs like the ATmega328PB.
// https://www.mikrocontroller.net/articles/Soft-PWM
// After the transmission is initiated, the first
// byte of the subsequent I2C transmission includes
// the 7-bit I2C device address 0x38 and a SDA
// direction bit.
// Soft reset device.
TWI_Start(0x38, 0);
TWI_Write(0xBA);
TWI_Wait_ACK();
TWI_Stop();
// Wait 40ms after power-on.
Sleep(40);
// Before reading the temperature and humidity
// values, first check whether the calibration
// enable bit Bit [3] of the status word is 1 (you
// can get a byte of status word by sending 0x71).
TWI_Start(0x38, 0);
TWI_Write(0x71);
TWI_Wait_ACK();
data = TWI_Read_NACK();
TWI_Stop();
Info("Received calibration status %02X.", data);
// If not 1, need to send 0xBE command (for
// initialization), this command parameter has two
// bytes, the first byte is 0x08, the second byte
// is 0x00, and then wait for 10ms.
if (data & ~BIT(3)) {
Info("Requesting calibration...");
TWI_Start(0x38, 0);
TWI_Write(0xBE);
TWI_Wait_ACK();
TWI_Write(0x08);
TWI_Wait_ACK();
TWI_Write(0x00);
TWI_Wait_ACK();
Sleep(10);
data = TWI_Read_NACK();
TWI_Stop();
if (data & ~BIT(3)) {
Info("Error: Calibration failed.");
return -1;
}
}
// Send the 0xAC command directly (trigger
// measurement). The parameter of this command has
// two bytes, the first byte is 0x33 and the second
// byte is 0x00.
Info("Triggering measurement...");
TWI_Start(0x38, 0);
TWI_Wait_ACK();
TWI_Write(0xAC);
TWI_Wait_ACK();
TWI_Write(0x33);
TWI_Wait_ACK();
TWI_Write(0x00);
TWI_Wait_ACK();
TWI_Stop();
// Wait for 80ms to wait for the measurement to be
// completed. If the read status word Bit [7] is 0,
// it indicates that the measurement is completed,
// and six bytes can be read in a row. Otherwise
// continue to wait.
Info("Reading measurement...");
TWI_Start(0x38, 1); // Read
TWI_Wait_ACK();
do {
Sleep(80);
data = TWI_Read_ACK();
} while (data & BIT(7));
data = TWI_Read_ACK();
Info("Received data byte %02X.", data);
data = TWI_Read_ACK();
Info("Received data byte %02X.", data);
data = TWI_Read_ACK();
Info("Received data byte %02X.", data);
data = TWI_Read_ACK();
Info("Received data byte %02X.", data);
data = TWI_Read_ACK();
Info("Received data byte %02X.", data);
data = TWI_Read_ACK();
Info("Received data byte %02X.", data);
// After receiving six bytes, the next byte is the
// CRC check data, the user can read it as needed,
// if the receiving end needs CRC check, then send
// it after receiving the sixth byte ACK response,
// otherwise NACK is sent out, CRC initial value is
// 0xFF. The CRC8 check polynomial is:
// CRC[7:0]= 1 + (x^4) + (x^5) + (x^8)
crc = TWI_Read_NACK();
Info("Received CRC8 byte %02X.", crc);
// Calculate the temperature and humidity values.
// Note: The calibration status check in the first
// step only needs to be checked at power-on. No
// operation is required during the normal
// acquisition process.
// TODO: Calculate values
TWI_Stop();
return 0;
}
int main(void)
int Init(void)
{
USART_Init();
sei();
@@ -154,22 +31,41 @@ int main(void)
PWM_SetValue(FAN02, 50);
PWM_SetValue(FAN03, 20);
// TODO: Set FAN03 timer frequency
// TODO: Implement ADS1115 and AHT20
TWI_SetChannel(AHT01);
TWI_AHT20_Init();
// TEM01, TEM02, TEM03
// HUM01, HUM02, HUM03
TWI_SetChannel(AHT02);
TWI_AHT20_Init();
// TWI_GetValue(TEM03)
// TWI_GetValue(HUM03)
TWI_SetChannel(AHT03);
TWI_AHT20_Init();
TWI_SetChannel(AHT01); // I2C Mux
TWI_ReadAHT20(); // TEMP and RH
return 0;
}
Info("Running idle loop...");
void Update(void)
{
float temp, rhum;
TWI_SetChannel(AHT01);
TWI_AHT20_Read(&temp, &rhum);
Info("TEMP=%.2f, RHUM=%.2f", temp, rhum);
TWI_SetChannel(AHT02);
TWI_AHT20_Read(&temp, &rhum);
Info("TEMP=%.2f, RHUM=%.2f", temp, rhum);
TWI_SetChannel(AHT03);
TWI_AHT20_Read(&temp, &rhum);
Info("TEMP=%.2f, RHUM=%.2f", temp, rhum);
}
int main(void)
{
Init();
for (;;) {
// Info("PING");
Update();
Sleep(1000);
}