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-rw-r--r--src/app/mhz19/Kconfig6
-rw-r--r--src/app/mhz19/Makefile.inc9
-rw-r--r--src/app/mhz19/main.cc173
3 files changed, 188 insertions, 0 deletions
diff --git a/src/app/mhz19/Kconfig b/src/app/mhz19/Kconfig
new file mode 100644
index 0000000..473cea9
--- /dev/null
+++ b/src/app/mhz19/Kconfig
@@ -0,0 +1,6 @@
+# Copyright 2020 Daniel Friesel
+#
+# SPDX-License-Identifier: CC0-1.0
+
+prompt "MH-Z19C reader"
+depends on arch_msp430fr5994lp && !meta_driver_stdin && loop && !wakeup
diff --git a/src/app/mhz19/Makefile.inc b/src/app/mhz19/Makefile.inc
new file mode 100644
index 0000000..0eea52a
--- /dev/null
+++ b/src/app/mhz19/Makefile.inc
@@ -0,0 +1,9 @@
+# vim:ft=make
+#
+# Copyright 2020 Daniel Friesel
+#
+# SPDX-License-Identifier: CC0-1.0
+
+ifdef app
+ loop = 1
+endif
diff --git a/src/app/mhz19/main.cc b/src/app/mhz19/main.cc
new file mode 100644
index 0000000..23c7984
--- /dev/null
+++ b/src/app/mhz19/main.cc
@@ -0,0 +1,173 @@
+/*
+ * Copyright 2021 Daniel 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 &copy);
+
+ 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 &copy);
+ 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;
+}