Parallel Digital READ/WRITE

This Repository consists of functions to read and write data to multiple pins with high speed on Teensy4.0 with the help of port manipulation.
It uses only breadboard friendly pins(0-23) and has been optimised to consume less time as much as possible.
The pins are optimised to take less memory and execution and should not be changed.
(*changing pins requires lot of changes in the code.)

There are 5 options for number of bits.

• 8 BIT
• 10 BIT
• 12 BIT
• 16 BIT
• 24 BIT

There are four operations for each option.

• set_xbit
• read_xbit
• write_xbit
• safe_write_xbit
  (where x can be 8,10,12,16 or 24.)

8 BIT pinmap:

PINS	PORT	INT_BIT	DATA_BIT
19	GPIO_6	16	0
18	GPIO_6	17	1
14	GPIO_6	18	2
15	GPIO_6	19	3
17	GPIO_6	22	4
16	GPIO_6	23	5
22	GPIO_6	24	6
23	GPIO_6	25	7

10 BIT pinmap:

PINS	PORT	INT_BIT	DATA_BIT
19	GPIO_6	16	0
18	GPIO_6	17	1
14	GPIO_6	18	2
15	GPIO_6	19	3
17	GPIO_6	22	4
16	GPIO_6	23	5
22	GPIO_6	24	6
23	GPIO_6	25	7
20	GPIO_6	26	8
21	GPIO_6	27	9

12 BIT pinmap:

PINS	PORT	INT_BIT	DATA_BIT
19	GPIO_6	16	0
18	GPIO_6	17	1
14	GPIO_6	18	2
15	GPIO_6	19	3
17	GPIO_6	22	4
16	GPIO_6	23	5
22	GPIO_6	24	6
23	GPIO_6	25	7
20	GPIO_6	26	8
21	GPIO_6	27	9
1	GPIO_6	2	10
0	GPIO_6	3	11

16 BIT pinmap:

PINS	PORT	INT_BIT	DATA_BIT
10	GPIO_7	0	0
12	GPIO_7	1	1
11	GPIO_7	2	2
13	GPIO_7	3	3
17	GPIO_6	22	4
16	GPIO_6	23	5
22	GPIO_6	24	6
23	GPIO_6	25	7
20	GPIO_6	26	8
21	GPIO_6	27	9
1	GPIO_6	2	10
0	GPIO_6	3	11
19	GPIO_6	16	12
18	GPIO_6	17	13
14	GPIO_6	18	14
15	GPIO_6	19	15

24 BIT pinmap:

PINS	PORT	INT_BIT	DATA_BIT
10	GPIO_7	0	0
12	GPIO_7	1	1
11	GPIO_7	2	2
13	GPIO_7	3	3
17	GPIO_6	22	4
16	GPIO_6	23	5
22	GPIO_6	24	6
23	GPIO_6	25	7
20	GPIO_6	26	8
21	GPIO_6	27	9
1	GPIO_6	2	10
0	GPIO_6	3	11
19	GPIO_6	16	12
18	GPIO_6	17	13
14	GPIO_6	18	14
15	GPIO_6	19	15
2	GPIO_9	4	16
3	GPIO_9	5	17
4	GPIO_9	6	18
5	GPIO_9	8	19
6	GPIO_7	10	20
9	GPIO_7	11	21
8	GPIO_7	16	22
7	GPIO_7	17	23

Setting pins :

set_xbit(mode);

x is no of bits and can be 8,10,12,16,24.
mode can be INPUT, INPUT_PULLUP, INPUT_PULLDOWN, OUTPUT....
this functions sets the pin as input/output it uses the usual pinMode() function with a for loop to set the pins.

Reading data :

read_xbit();

it returns the value of the data read on the pins as an unsigned integer of suitable size. Assign its value to a variable in the code.

No_of_bits	type_of_return_value	No_of_ports	Speed
8	uint8_t	1	14ns
10	uint16_t	1	14ns
12	uint16_t	1	14ns
16	uint16_t	2	26~27ns
24	uint32_t	3	40ns

you can see that number of ports affects the speed so using less no of ports is recommonded.
*16-bit and and 24-bit can be reduced to 14ns and 27ns by using pins on the backside of the board(24,25,26,27 to be specific).

Writing data:

write_xbit(data);

x is no of bits and can be 8,10,12,16,24.
data is the parameter to be written on the data line.
This mode is faster compared to safe_write() but this method might affect other pins on the port if not managed properly.

No_of_bits	parameter_type	No_of_ports	Speed	Pins_that_might_get_affected
8	uint8_t	1	3ns	0,1,20,21,24,25,26,27
10	uint16_t	1	3ns	0,1,24,25,26,27
12	uint16_t	1	3ns	24,25,26,27
16	uint16_t	2	6~7ns	24,25,26,27,6,7,8,9,32
24	uint32_t	3	10ns	24,25,26,27,29,32,33

Again number of ports affects the speed. Speed of 16-bit and 24-bit speed can be improved to 3ns and 7ns by using pins on the backside of the board(24,25,26,27 to be specific).

safe_write_xbit(data);

This method is same as write but it doesn't affect other pins.
But it does it at the cost of the speed.

No_of_bits	Speed
8	23ns
10	23ns
12	23ns
16	43ns
24	70ns

Once again Speed of 16-bit and 24-bit speed can be improved to 23ns and 43ns by using pins on the backside of the board(24,25,26,27 to be specific).
*The speed is calculated by executing the instruction 1000 times and measuring the time taken It might not be accurate. I would like to see if anyone can probe the pins with oscilloscope and measure the speed.