Add initial temperature reading via DS18B20 device

Actually plumb the 1-Wire support into the temperature query and
use an attached DS18B20 to retrieve the current temperature. This
*mostly* works with the existing TEMPer clients but there are
occasional USB issues, I think due to timing on the 1-Wire delays
affecting USB responses.

diff --git a/main.c b/main.c
index 9899cb90ef2556bf4e18f1fda89e8847a79c405c..0adfed8cc246c636c0180b32bffe295d9fdc20ca 100644 (file)
--- a/main.c
+++ b/main.c
@@ -39,6 +39,8 @@ typedef struct {
 } keyboard_report_t;
 keyboard_report_t keyboard_report;
 
+uint8_t temp_state = 0;
+
 uint8_t temp_report[8];
 bool have_temp_int = false;
 
@@ -216,6 +218,36 @@ void set_serial(void)
        }
 }
 
+uint16_t read_temp(void)
+{
+       uint8_t buf[9];
+
+       cli();
+       if (!w1_reset()) {
+               return 0xFFFF;
+               sei();
+       }
+
+       w1_write(0xCC);         /* SKIP ROM */
+       w1_write(0x44);         /* Convert T */
+
+       do {
+               w1_read(buf, 1);
+       } while (buf[0] != 0xFF);
+
+       if (!w1_reset()) {
+               return 0xFFFF;
+               sei();
+       }
+
+       w1_write(0xCC);         /* SKIP ROM */
+       w1_write(0xBE);         /* Read Scratchpad */
+       w1_read(buf, 9);
+       sei();
+
+       return buf[2] << 8 | buf[1];
+}
+
 usbMsgLen_t usbFunctionDescriptor(usbRequest_t *rq)
 {
        if (rq->wValue.bytes[1] == USBDESCR_STRING &&
@@ -282,6 +314,7 @@ usbMsgLen_t usbFunctionSetup(uchar data[8])
 usbMsgLen_t usbFunctionWrite(uint8_t * data, uchar len)
 {
        if (len == 1) {
+               PORTB |= 1 << PB1; // LED on
                if (data[0] != ledstate) {
                        ledstate = data[0];
 
@@ -301,13 +334,10 @@ usbMsgLen_t usbFunctionWrite(uint8_t * data, uchar len)
 
                if (data[1] == 0x80 && data[2] == 0x33 && data[3] == 1) {
                        /* Temperature query */
-                       have_temp_int = true;
+                       memset(temp_report, 0, 8);
+                       temp_state = 1;
                        temp_report[0] = 0x80;
                        temp_report[1] = 2;
-                       /* Fake 15°C */
-                       temp_report[2] = 0xF;
-                       temp_report[3] = 0x0;
-
                } else if (data[1] == 0x82 && data[2] == 0x77 &&
                                data[3] == 1) {
                        /* Initialisation Query #1 */
@@ -331,6 +361,7 @@ usbMsgLen_t usbFunctionWrite(uint8_t * data, uchar len)
 int main(void)
 {
        unsigned char i;
+       uint8_t buf[9];
 
        wdt_enable(WDTO_1S);
 
@@ -371,5 +402,48 @@ int main(void)
                                have_temp_int = false;
                        }
                }
+
+               if (temp_state == 1) {
+                       if (w1_reset()) {
+                               temp_state = 2;
+                       } else {
+                               temp_report[2] = 0xFF;
+                               temp_report[3] = 0xFF;
+                               have_temp_int = true;
+                               temp_state = 0;
+                       }
+               } else if (temp_state == 2) {
+                       w1_write(0xCC);         /* SKIP ROM */
+                       temp_state = 3;
+               } else if (temp_state == 3) {
+                       w1_write(0x44);         /* Convert T */
+                       temp_state = 4;
+               } else if (temp_state == 4) {
+                       if (w1_read_byte() == 0xFF)
+                               temp_state = 5;
+               } else if (temp_state == 5) {
+                       if (w1_reset()) {
+                               temp_state = 6;
+                       } else {
+                               temp_report[2] = 0xFF;
+                               temp_report[3] = 0xFE;
+                               have_temp_int = true;
+                               temp_state = 0;
+                       }
+               } else if (temp_state == 6) {
+                       w1_write(0xCC);         /* SKIP ROM */
+                       temp_state = 7;
+               } else if (temp_state == 7) {
+                       w1_write(0xBE);         /* Read Scratchpad */
+                       temp_state = 8;
+               } else if (temp_state > 7 && temp_state < 17) {
+                       buf[temp_state - 8] = w1_read_byte();
+                       temp_state++;
+               } else if (temp_state == 17) {
+                       temp_report[2] = buf[1] << 4 | buf[0] >> 4;
+                       temp_report[3] = buf[0] << 4;
+                       have_temp_int = true;
+                       temp_state = 0;
+               }
        }
 }