43oh

# Nisarg

Members

6

## Reputation Activity

1.
TI has some sample code for the internal temperature sensor, but it does not explain how to scale the ADC reading to useful units of degrees. Here is a step-by-step explanation of how to do the scaling with integer math for degrees C, K and F. There is also sample code to display the temperature on a Nokia 5110 LCD.

The data sheet (SLAU144) has this formula for converting temperature in degrees Celsius to voltage.
V = 0.00355 * C + 0.986

What we need is a formula for converting voltage to temperature.

Rewrite the data sheet fomula with temperature on the left
0.00355 * C + 0.986 = V

Divide both sides by 0.00355
C + 277.75 = V / 0.00355

Subtract 277.75 from both sides
C = V / 0.00355 - 277.75

Now we have a formula for converting voltage to temperature.

The data sheet has this formula for converting voltage to ADC value, once again the opposite of what we neeed.

For Vref- == 0
A = 1023 * V / Vref

Swap sides
1023 * V / Vref = A

Multiply by Vref
1023 * V = A * Vref

Divide by 1023
V = A * Vref / 1023

For a 1.5V reference
V = A * 1.5 / 1023

Simplify
V = A * 0.0014663

Substitute ADC conversion forumula for voltage in the temperature conversion formula.
C = A * 0.0014663 / 0.00355 - 277.75

Simplify
C = A * 0.413 - 277.75

It uses real numbers, so floating point math is required for good precision.
Floating point is slow and requires more flash, so let's use integer math instead.
Multiply by 65536 (2^16) and then divide by the same.
C = (A * 27069 - 18202393) / 65536

Use a right shift instead of divide. This will become a move of high word to low word.
C = (A * 27069 - 18202393) >> 16

Add 0.5 * 65536 to impove rounding.
C = (A * 27069 - 18202393 + 32768) >> 16

Simplify.
C = (A * 27069 - 18169625) >> 16

So that is how to go from ADC to degrees Celsius.

To convert degrees C to degees K.
K = C + 273.15

Applied to ADC to degrees C conversion formula.
K = (A * 27069 - 18169625) >> 16 - 273.15

Implement with integer math by multiplying by 65536
K = (A * 27069 - 18169625 - 17,901,158) >> 16

Simplify.
K = (A * 27069 - 268467) >> 16

To convert degrees C to degrees F.
F = C * 9 / 5 + 32

Applied to voltage to degrees C conversion forumula
F = (V / 0.00355 - 277.75) * 9 / 5 + 32

Multiply by 9
F = (V / 0.0003944 - 2499.75) / 5 + 32

Divide by 5
F = (V / 0.0019722 - 499.95) + 32

F = V / 0.0019722 - 467.95

F = A * 0.0014663 / 0.0019722 - 467.95

Simplifiy
F = A * 0.7435 - 467.95

Convert to integer
F = (A * 48724 - 30667156) >> 16

Improve rounding
F = (A * 48724 - 30667156 + 32768) >> 16

Simplify
F = (A * 48724 - 30634388) >> 16

So now we have three formulas to convert ADC reading to degrees C, K and F using fast and compact integer math.
C = (A * 27069 - 18169625) >> 16
K = (A * 27069 - 268467) >> 16
F = (A * 48724 - 30634388) >> 16

Using the ADC value, rather than a different temperature scale, will ensure greatest precision for each temperature scale.

main.c

lcd.h

typedef enum { lcd_command = 0, // Array of one or more commands lcd_data = 1, // Array of one or more bytes of data lcd_data_repeat = 2 // One byte of data repeated } lcd_cmd_type; void lcd_send(const unsigned char *cmd, unsigned len, const lcd_cmd_type type); void lcd_home(void); void lcd_pos(unsigned char x, unsigned char y); void lcd_clear(unsigned char x); void lcd_init(void); void lcd_print(char *s, unsigned x, unsigned y); void pd12(unsigned n, unsigned x, unsigned y);

lcd.c

#include #include "lcd.h" //static const unsigned TXD = BIT1; static const unsigned RXD = BIT2; static const unsigned SWITCH = BIT3; static const unsigned LCD_CLK = BIT5; static const unsigned LCD_BACKLIGHT = BIT6; static const unsigned LCD_DATA = BIT7; static const unsigned LCD_DC = BIT0; // PORT2 static const unsigned LCD_CE = BIT1; // PORT2 void lcd_send(const unsigned char *cmd, unsigned len, const lcd_cmd_type type) { register unsigned mask; P2OUT &= ~LCD_CE; do { mask = 0x0080; do { if(*cmd & mask) { P1OUT &= ~LCD_CLK; P1OUT |= LCD_DATA; } else { P1OUT &= ~(LCD_CLK | LCD_DATA); } P1OUT |= LCD_CLK; mask >>= 1; } while(!(mask & 1)); if(!type) P2OUT &= ~LCD_DC; if(*cmd & mask) { P1OUT &= ~LCD_CLK; P1OUT |= LCD_DATA; } else { P1OUT &= ~(LCD_CLK | LCD_DATA); } P1OUT |= LCD_CLK; P2OUT |= LCD_DC; if(!(type & 2)) ++cmd; } while(--len); P2OUT |= LCD_CE; } static const unsigned char home[] = { 0x40, 0x80 }; void lcd_home(void) { lcd_send(home, sizeof(home), lcd_command); } void lcd_pos(unsigned char x, unsigned char y) { unsigned char c[2]; c[0] = 0x80 | x; c[1] = 0x40 | y; lcd_send(c, sizeof(c), lcd_command); } void lcd_clear(unsigned char x) { lcd_home(); lcd_send(&x, 504, lcd_data_repeat); lcd_home(); } void lcd_init(void) { static const unsigned char init[] = { 0x20 + 0x01, // function set - extended instructions enabled //0x80 + 64, // set vop (contrast) 0 - 127 0x80 + 66, // set vop (contrast) 0 - 127 0x04 + 0x02, // temperature control 0x10 + 0x03, // set bias system 0x20 + 0x00, // function set - chip active, horizontal addressing, basic instructions 0x08 + 0x04 // display control - normal mode }; P1REN = RXD | SWITCH; P1DIR = LCD_CLK | LCD_BACKLIGHT | LCD_DATA; P1OUT = LCD_CLK | RXD | SWITCH | LCD_BACKLIGHT; P2REN = 0; P2DIR = LCD_DC | LCD_CE; P2OUT = LCD_CE; __delay_cycles(20000); P2OUT |= LCD_DC; __delay_cycles(20000); lcd_send(init, sizeof(init), lcd_command); } static const unsigned char font6x8[96][5] = { 0x00, 0x00, 0x00, 0x00, 0x00, // 20 32 0x00, 0x00, 0x5F, 0x00, 0x00, // 21 33 ! 0x00, 0x07, 0x00, 0x07, 0x00, // 22 34 " 0x14, 0x7F, 0x14, 0x7F, 0x14, // 23 35 # 0x24, 0x2A, 0x7F, 0x2A, 0x12, // 24 36 \$ 0x23, 0x13, 0x08, 0x64, 0x62, // 25 37 % 0x36, 0x49, 0x56, 0x20, 0x50, // 26 38 & 0x00, 0x08, 0x07, 0x03, 0x00, // 27 39 ' 0x00, 0x1C, 0x22, 0x41, 0x00, // 28 40 ( 0x00, 0x41, 0x22, 0x1C, 0x00, // 29 41 ) 0x2A, 0x1C, 0x7F, 0x1C, 0x2A, // 2A 42 * 0x08, 0x08, 0x3E, 0x08, 0x08, // 2B 43 + 0x00, 0x40, 0x38, 0x18, 0x00, // 2C 44 , 0x08, 0x08, 0x08, 0x08, 0x08, // 2D 45 - 0x00, 0x00, 0x60, 0x60, 0x00, // 2E 46 . 0x20, 0x10, 0x08, 0x04, 0x02, // 2F 47 / 0x3E, 0x51, 0x49, 0x45, 0x3E, // 30 48 0 0x00, 0x42, 0x7F, 0x40, 0x00, // 31 49 1 0x42, 0x61, 0x51, 0x49, 0x46, // 32 50 2 0x21, 0x41, 0x49, 0x4D, 0x33, // 33 51 3 0x18, 0x14, 0x12, 0x7F, 0x10, // 34 52 4 0x27, 0x45, 0x45, 0x45, 0x39, // 35 53 5 0x3C, 0x4A, 0x49, 0x49, 0x30, // 36 54 6 0x41, 0x21, 0x11, 0x09, 0x07, // 37 55 7 0x36, 0x49, 0x49, 0x49, 0x36, // 38 56 8 0x06, 0x49, 0x49, 0x29, 0x1E, // 39 57 9 0x00, 0x00, 0x14, 0x00, 0x00, // 3A 58 : 0x00, 0x00, 0x40, 0x34, 0x00, // 3B 59 ; 0x00, 0x08, 0x14, 0x22, 0x41, // 3C 60 < 0x14, 0x14, 0x14, 0x14, 0x14, // 3D 61 = 0x00, 0x41, 0x22, 0x14, 0x08, // 3E 62 > 0x02, 0x01, 0x51, 0x09, 0x06, // 3F 63 ? 0x3E, 0x41, 0x5D, 0x59, 0x4E, // 40 64 @ 0x7C, 0x12, 0x11, 0x12, 0x7C, // 41 65 A 0x7F, 0x49, 0x49, 0x49, 0x36, // 42 66 B 0x3E, 0x41, 0x41, 0x41, 0x22, // 43 67 C 0x7F, 0x41, 0x41, 0x41, 0x3E, // 44 68 D 0x7F, 0x49, 0x49, 0x49, 0x41, // 45 69 E 0x7F, 0x09, 0x09, 0x09, 0x01, // 46 70 F 0x3E, 0x41, 0x49, 0x49, 0x7A, // 47 71 G 0x7F, 0x08, 0x08, 0x08, 0x7F, // 48 72 H 0x00, 0x41, 0x7F, 0x41, 0x00, // 49 73 I 0x20, 0x40, 0x41, 0x3F, 0x01, // 4A 74 J 0x7F, 0x08, 0x14, 0x22, 0x41, // 4B 75 K 0x7F, 0x40, 0x40, 0x40, 0x40, // 4C 76 L 0x7F, 0x02, 0x1C, 0x02, 0x7F, // 4D 77 M 0x7F, 0x04, 0x08, 0x10, 0x7F, // 4E 78 N 0x3E, 0x41, 0x41, 0x41, 0x3E, // 4F 79 O 0x7F, 0x09, 0x09, 0x09, 0x06, // 50 80 P 0x3E, 0x41, 0x51, 0x21, 0x5E, // 51 81 Q 0x7F, 0x09, 0x19, 0x29, 0x46, // 52 82 R 0x26, 0x49, 0x49, 0x49, 0x32, // 53 83 S 0x01, 0x01, 0x7F, 0x01, 0x01, // 54 84 T 0x3F, 0x40, 0x40, 0x40, 0x3F, // 55 85 U 0x1F, 0x20, 0x40, 0x20, 0x1F, // 56 86 V 0x3F, 0x40, 0x38, 0x40, 0x3F, // 57 87 W 0x63, 0x14, 0x08, 0x14, 0x63, // 58 88 X 0x03, 0x04, 0x78, 0x04, 0x03, // 59 89 Y 0x61, 0x51, 0x49, 0x45, 0x43, // 5A 90 Z 0x00, 0x7F, 0x41, 0x41, 0x41, // 5B 91 [ 0x02, 0x04, 0x08, 0x10, 0x20, // 5C 92 '\' 0x00, 0x41, 0x41, 0x41, 0x7F, // 5D 93 ] 0x04, 0x02, 0x01, 0x02, 0x04, // 5E 94 ^ 0x80, 0x80, 0x80, 0x80, 0x80, // 5F 95 _ 0x00, 0x03, 0x07, 0x08, 0x00, // 60 96 ' 0x20, 0x54, 0x54, 0x54, 0x78, // 61 97 a 0x7F, 0x28, 0x44, 0x44, 0x38, // 62 98 b 0x38, 0x44, 0x44, 0x44, 0x28, // 63 99 c 0x38, 0x44, 0x44, 0x28, 0x7F, // 64 100 d 0x38, 0x54, 0x54, 0x54, 0x18, // 65 101 e 0x00, 0x08, 0x7E, 0x09, 0x02, // 66 102 f 0x18, 0xA4, 0xA4, 0xA4, 0x7C, // 67 103 g 0x7F, 0x08, 0x04, 0x04, 0x78, // 68 104 h 0x00, 0x44, 0x7D, 0x40, 0x00, // 69 105 i 0x00, 0x20, 0x40, 0x40, 0x3D, // 6A 106 j 0x00, 0x7F, 0x10, 0x28, 0x44, // 6B 107 k 0x00, 0x41, 0x7F, 0x40, 0x00, // 6C 108 l 0x7C, 0x04, 0x78, 0x04, 0x78, // 6D 109 m 0x7C, 0x08, 0x04, 0x04, 0x78, // 6E 110 n 0x38, 0x44, 0x44, 0x44, 0x38, // 6F 111 o 0xFC, 0x18, 0x24, 0x24, 0x18, // 70 112 p 0x18, 0x24, 0x24, 0x18, 0xFC, // 71 113 q 0x7C, 0x08, 0x04, 0x04, 0x08, // 72 114 r 0x48, 0x54, 0x54, 0x54, 0x24, // 73 115 s 0x04, 0x04, 0x3F, 0x44, 0x24, // 74 116 t 0x3C, 0x40, 0x40, 0x20, 0x7C, // 75 117 u 0x1C, 0x20, 0x40, 0x20, 0x1C, // 76 118 v 0x3C, 0x40, 0x30, 0x40, 0x3C, // 77 119 w 0x44, 0x28, 0x10, 0x28, 0x44, // 78 120 x 0x4C, 0x90, 0x90, 0x90, 0x7C, // 79 121 y 0x44, 0x64, 0x54, 0x4C, 0x44, // 7A 122 z 0x00, 0x08, 0x36, 0x41, 0x00, // 7B 123 { 0x00, 0x00, 0x77, 0x00, 0x00, // 7C 124 | 0x00, 0x41, 0x36, 0x08, 0x00, // 7D 125 } 0x02, 0x01, 0x02, 0x04, 0x02, // 7E 126 ~ 0x00, 0x06, 0x09, 0x09, 0x06, // 7F 127 degrees }; void lcd_print(char *s, unsigned x, unsigned y) { unsigned char c[2]; c[0] = 0x80 | x; c[1] = 0x40 | y; lcd_send(c, sizeof(c), lcd_command); while(*s) { lcd_send(&font6x8[*s - 32][0], 5, lcd_data); lcd_send(&font6x8[0][0], 1, lcd_data); ++s; } } static const unsigned char num11x16[19][11 * 2] = { 0x00,0xF0,0xFC,0xFE,0x06,0x02,0x06,0xFE,0xFC,0xF0,0x00, // 0 0x00,0x07,0x1F,0x3F,0x30,0x20,0x30,0x3F,0x1F,0x07,0x00, 0x00,0x00,0x08,0x0C,0xFC,0xFE,0xFE,0x00,0x00,0x00,0x00, // 1 0x00,0x20,0x20,0x20,0x3F,0x3F,0x3F,0x20,0x20,0x20,0x00, 0x00,0x0C,0x0E,0x06,0x02,0x02,0x86,0xFE,0x7C,0x38,0x00, // 2 0x00,0x30,0x38,0x3C,0x36,0x33,0x31,0x30,0x30,0x38,0x00, 0x00,0x0C,0x0E,0x86,0x82,0x82,0xC6,0xFE,0x7C,0x38,0x00, // 3 0x00,0x18,0x38,0x30,0x20,0x20,0x31,0x3F,0x1F,0x0E,0x00, 0x00,0x00,0xC0,0x20,0x18,0x04,0xFE,0xFE,0xFE,0x00,0x00, // 4 0x00,0x03,0x02,0x02,0x02,0x22,0x3F,0x3F,0x3F,0x22,0x02, 0x00,0x00,0x7E,0x7E,0x46,0x46,0xC6,0xC6,0x86,0x00,0x00, // 5 0x00,0x18,0x38,0x30,0x20,0x20,0x30,0x3F,0x1F,0x0F,0x00, 0x00,0xC0,0xF0,0xF8,0xFC,0x4C,0xC6,0xC2,0x82,0x00,0x00, // 6 0x00,0x0F,0x1F,0x3F,0x30,0x20,0x30,0x3F,0x1F,0x0F,0x00, 0x00,0x06,0x06,0x06,0x06,0x06,0xC6,0xF6,0x3E,0x0E,0x00, // 7 0x00,0x00,0x00,0x30,0x3C,0x0F,0x03,0x00,0x00,0x00,0x00, 0x00,0x38,0x7C,0xFE,0xC6,0x82,0xC6,0xFE,0x7C,0x38,0x00, // 8 0x00,0x0E,0x1F,0x3F,0x31,0x20,0x31,0x3F,0x1F,0x0E,0x00, 0x00,0x78,0xFC,0xFE,0x86,0x02,0x86,0xFE,0xFC,0xF8,0x00, // 9 0x00,0x00,0x00,0x21,0x21,0x31,0x1D,0x1F,0x0F,0x03,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, // 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x70,0x70,0x70,0x00,0x00,0x00,0x00,0x00,0x00,0x00, // : 0x00,0x0E,0x0E,0x0E,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, // . 0x00,0x38,0x38,0x38,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0xC0,0x30,0x0C,0x00,0x00,0x00,0x00, // / 0x00,0x30,0x0C,0x03,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x80, // - 0x00,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01, 0x00,0x18,0x3C,0x66,0x66,0x3C,0x18,0x00,0x00,0x00,0x00, // 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0xF0,0xF8,0x0C,0x06,0x02,0x02,0x02,0x02,0x0E,0x0C,0x00, // C 0x03,0x07,0x0C,0x18,0x10,0x10,0x10,0x10,0x1C,0x0C,0x00, 0xFE,0xFE,0x42,0x42,0x42,0x42,0x42,0x42,0x00,0x00,0x00, // F 0x1F,0x1F,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0xFE,0xFE,0x40,0xE0,0xB0,0x18,0x0C,0x06,0x02,0x00,0x00, // K 0x1F,0x1F,0x00,0x00,0x01,0x03,0x06,0x0C,0x18,0x10,0x00 }; void pd12(unsigned n, unsigned x, unsigned y) { unsigned char c[2]; c[0] = 0x80 | x; c[1] = 0x40 + y; lcd_send(c, 2, lcd_command); lcd_send(num11x16[n], 11, lcd_data); c[1] = 0x41 + y; lcd_send(c, 2, lcd_command); lcd_send(num11x16[n] + 11, 11, lcd_data); }
2.
I am an Arduino user and just discovered Energia for the MSP430.  After installing Energia on my MacBook Pro (Snow Leopard 10.6.8) and following the Getting Starting steps, I loaded the Blink sketch.  Upon compiling I get this error:

....Energia.app/Contents/Resources/Java/hardware/tools/msp430/bin/../lib/gcc/msp430/4.6.3/../../../../msp430/bin/ld: cannot open linker script file memory.x: No such file or directory collect2: ld returned 1 exit status   This must be pretty trivial, because I cannot find anything about this in this forum.  I am hoping someone can enlighten me. Thanks Herbert
×
• Blog

• #### Activity

×
• Create New...