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/*
* Copyright 2021 Birte Kristina Friesel
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "arch.h"
#include "driver/gpio.h"
#include "driver/stdout.h"
class SerialOutput : public OutputStream {
private:
SerialOutput(const SerialOutput ©);
public:
SerialOutput () {}
void setup();
virtual void put(char c) override;
};
/*
* Baud rate calculation according to datasheet:
* N := f_{BRCLK} / Baudrate = F_CPU / 115200 in our case
* if N <= 16: OS16 = 0, UCBR0 = int(N)
* if N > 16: OS16 = 1, UCBR0 = int(N/16), UCBRF0 = int(((n/16) - int(n/16)) * 16) = int(N)%16
* Set UCBRS0 according to table 21-4
*/
void SerialOutput::setup()
{
UCA1CTLW0 |= UCSWRST;
#if F_CPU == 16000000UL
// 16M / 9600 == 1666.6667 -> UCOS16 = 1, UCBR0 = 104, UCBRF0 = 2, UCBRS0 = 0xd6 ("0.6667")
UCA1CTLW0 = UCSWRST | UCSSEL__SMCLK;
UCA1MCTLW = UCOS16 | (2<<4) | 0xd600;
UCA1BR0 = 104;
#elif F_CPU == 8000000UL
// 8M / 9600 == 833.3333 -> UCOS16 = 1, UCBR0 = 52, UCBRF0 = 1, UCBRS0 = 0x49 ("0.3335")
UCA1CTLW0 = UCSWRST | UCSSEL__SMCLK;
UCA1MCTLW = UCOS16 | (1<<4) | 0x4900;
UCA1BR0 = 52;
#else
#error Unsupported F_CPU
#endif
UCA1IRCTL = 0;
UCA1ABCTL = 0;
P2REN &= ~(BIT5 | BIT6);
P2SEL0 &= ~(BIT5 | BIT6);
P2SEL1 |= BIT5 | BIT6;
UCA1CTLW0 &= ~UCSWRST;
//UCA1IE |= UCRXIE;
}
void SerialOutput::put(char c)
{
while (!(UCA1IFG & UCTXIFG));
UCA1TXBUF = c;
if (c == '\n') {
put('\r');
}
}
SerialOutput sout;
class SerialInput {
private:
SerialInput(const SerialInput ©);
char buffer[64];
volatile unsigned char write_pos, read_pos;
public:
SerialInput() : write_pos(0), read_pos(0) {}
void setup();
bool hasKey();
char getKey();
inline void addKey(char key) {
buffer[write_pos++] = key;
write_pos %= 64;
}
};
void SerialInput::setup()
{
UCA1IE |= UCRXIE;
}
bool SerialInput::hasKey()
{
if (write_pos != read_pos) {
return true;
}
return false;
}
char SerialInput::getKey()
{
char ret = buffer[read_pos++];
read_pos %= 64;
return ret;
}
SerialInput sin;
__attribute__((interrupt(USCI_A1_VECTOR))) __attribute__((wakeup)) void handle_stdin()
{
if (UCA1IFG & UCRXIFG) {
sin.addKey(UCA1RXBUF);
}
}
const unsigned char mhz19c_read[] = {0xff, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
void loop(void)
{
static unsigned int interval = 0;
static char buf[9];
unsigned char i;
unsigned int co2_ppm;
signed int temperature;
unsigned int unknown_status;
unsigned int unknown_cal;
if (interval++ == 2) {
gpio.led_on(0);
for (i = 0; i < sizeof(mhz19c_read); i++) {
sout.put(mhz19c_read[i]);
}
arch.sleep_ms(100);
buf[1] = 0;
for (i = 0; i < 9; i++) {
if (sin.hasKey()) {
buf[i] = sin.getKey();
} else {
break;
}
}
if (i == 9) {
if (buf[0] == 0xff && buf[1] == 0x86) {
// see https://revspace.nl/MHZ19#Command_0x86_.28read_concentration.29
co2_ppm = (buf[2] << 8) + buf[3];
temperature = buf[4] - 40;
unknown_status = buf[5];
unknown_cal = (buf[6] << 8) + buf[7];
kout << "CO₂: " << co2_ppm << " ppm @ " << temperature << " °c ";
kout << unknown_status << " / " << unknown_cal << endl;
} else {
kout << "! communication error, expected 0xff 0x86, got" << hex << (int)buf[0] << ' ' << (int)buf[1] << dec << endl;
}
} else {
kout << "! timeout" << endl;
}
gpio.led_off(0);
interval = 0;
}
}
int main(void)
{
arch.setup();
gpio.setup();
kout.setup();
sout.setup();
sin.setup();
arch.idle_loop();
return 0;
}
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