12. DIGITAL I/O

This page describes the Digital I/Os present on the Floyd SC carrier card

Floyd SC Carrier card provides 16 GPIOs optionally exposed on the front panel at connector. Refer to for connector pinouts.

The DIOs on the Floyd SC Carrier card is realized using I2C to GPIO expander.

The I2C GPIO expander can be addressed at 0x22 on the I2C bus. The I2C bus number depends upon the module installed as tabulated below:

Floyd SC NX

The I2C GPIO expander can be addressed at 0x22 on on the bus /dev/i2c-8

Floyd SC Nano

The I2C GPIO expander can be addressed at 0x22 on on the bus /dev/i2c-8

12.1 Digital I/O Specifications

The DIOs on Floyd SC are 3.3V/5V voltage selectable output compliant tolerant. The logic specifications are as follows:

Digital I/O Specifications
Device	PCA9535
Number of Lines	16
Direction	Programmable bit by bit
Logic levels	3.3V/5V configurable
Pull resistors	10K ohms +/-1%; Jumper-selectable pull-up/down
Input voltage
Logic 0:	-0.5V min, 0.99V(3.3V Vio), 1.5V(5V Vio) max
Logic 1	2.64V(3.3V Vio)/ 3.5V(5V Vio) min, 5.5V max
Output Voltage
Logic 0:	0.0V min; 0.7V max @ 10mA output current
Logic 1	2.5V(3.3V Vio)/4V(5V Vio) min @ -10mA output current; 3.3V/5V max

Since the DIOs are realized with GPIO expanders, the DIOs do not provide any alternate functions but can only be used to drive logic high & logic low.

12.2 Software Commands

There are 4 commands to use the DIOs. They are as follows:

1. gpio_util setdir

This command configures the direction of a particular DIO. For example, to set DIO 3 as an input & DIO 4 as an output, follow the command as provided below:

gpio_util setdir 3 in // sets DIO 3 as an input
gpio_util setdir 4 out // sets DIO 4 as an output 

2. gpio_util getdir

This command reads the direction of a particular DIO. For example, to read the direction of DIO 2 (earlier set as an input) & DIO 5 (earlier set as an output), use the command as follows:

gpio_util getdir 2 //read direction of GPIO port 2
in // Prints out GPIO port 2 direction
gpio_util getdir 5 //read direction of GPIO port 5
out // Prints out GPIO port 2 direction

3. gpio_util setval

This command configures the logic driven to an output. For example, to drive a logic 0 to DIO 2 & a logic 1 to DIO 5, use the command as follows:

gpio_util setval 2 0 // drives DIO 2 as logic 0
gpio_util setval 5 1 // drives DIO 5 as logic 1 

4. gpio_util getval

This command reads the logic at an input pin. For example, to read the logic value at DIO 6, use the command as follows:

gpio_util getval 6 // reads the logic of DIO 6
0 // prints the logic level of DIO 

Total number of allowed GPIO numbers are 1-16.