On Tuesday, September 10, 2019, 10:27:08 AM EDT, Олег Бахарев <disconnec...@gmail.com> wrote: > Need man page for this.
My bad. I thought I had sent man pages along with the code. I've included the man page for it at the bottom of this message. > Can you get some example for reading/writing GPIO ? I've also included a short example that uses both the GPIO and the SPI interface to talk to a little Nokia LCD screen. BLS .TH GPIO 3 .SH NAME gpio \- access to Raspberry Pi GPIO pins .SH SYNOPSIS .B bind -a #G /dev .PP .B /dev/gpio .fi .SH DESCRIPTION .I Gpio serves a single file that provides access to the GPIO pins on the Raspberry Pi. Reads from the file receive a 16-character hexadecimal string representing a .B vlong giving the values of up to 64 GPIO lines. (The processor on both the first and second generation Pis provides 54 actual GPIO lines.) The proper method for sampling GPIO 27 is as follows: .IP .B read(gfd, buf, 16); .br .B buf[16] = 0; .br .B gvals = strtoull(buf, nil, 16); .br .B "pin27 = gvals & (1 << 27);" .PP Writes to .B gpio control the characteristics and output values of GPIO lines. The exact operation is specified by one of the following commands: .TP .BI function " pin f" Set the function of GPIO .I pin to .I f. The valid values for .I f are: .BR in , .BR out , .BR alt0 , .BR alt1 , .BR alt2 , .BR alt3 , .BR alt4 , .BR atl5 , and .BR pulse . The functions .B in and .B out set the specified GPIO line to be a general purpose input and output, respectively. The various .BI alt n functions are as specified in the Broadcom documentation and differ on a per-pin basis. The .B pulse function is somewhat specialized. It causes the pin to be set to an output for 2μS and then to be set to a input. With the value of the line set to 0 and a pullup resistor on the line, this operation provides a short low pulse suitable for bit-banging a 1-wire interface. .TP .BI pullup " pin" Enables the internal pullup resistor for the specified GPIO pin. .TP .BI pulldown " pin" Enables the internal pulldown resistor for the specified GPIO pin. .TP .BI float " pin" Disables both internal pullup and pulldown resistors for the specified GPIO pin. .TP .BI set " pin value" For GPIO pins set to the output function, this command sets the output value for the pin. The .I value should be either 0 or 1. .SH NOTES All pin number references are according to the SoC documentation. These GPIO signal numbers do .I not match the pin numbers on the header on the Pi board. Reads sample the external signal values. As a result, the values read for output pins might not match the value written to them if externally they are driven harder than the SoC drives them. .SH SOURCE .B /sys/src/9/bcm/devgpio.c .br .B /sys/src/9/bcm/gpio.c #include <u.h> #include <libc.h> void main() { int gfd, sfd, i, j; uchar buf[256]; gfd = open("/dev/gpio", ORDWR); sfd = open("/dev/spi0", ORDWR); if(gfd < 0 || sfd < 0) print("open error: %r\n"); fprint(gfd, "function 22 out"); fprint(gfd, "set 22 0"); sleep(1); fprint(gfd, "set 22 1"); fprint(gfd, "function 27 out"); fprint(gfd, "function 26 out"); fprint(gfd, "set 26 1"); sleep(10); fprint(gfd, "set 26 0"); fprint(gfd, "set 27 0"); sleep(1); buf[0] = 0x21; pwrite(sfd, buf, 1, 0); sleep(1); buf[0] = 0x14; pwrite(sfd, buf, 1, 0); sleep(1); buf[0] = 0xc0; pwrite(sfd, buf, 1, 0); sleep(1); buf[0] = 0x20; if(pwrite(sfd, buf, 1, 0) < 0) print("write error: %r\n"); sleep(1); buf[1] = 0x0c; if(pwrite(sfd, buf+1, 1, 0) < 0) print("write error: %r\n"); sleep(1); buf[2] = 0x40; if(pwrite(sfd, buf+2, 1, 0) < 0) print("write error: %r\n"); sleep(1); buf[3] = 0x80; if(pwrite(sfd, buf+3, 1, 0) < 0) print("write error: %r\n"); // pwrite(sfd, buf, 4, 0); fprint(gfd, "set 27 1"); for(j = 0; j < 256; ++j) { for(i = 0; i < 16; ++i) buf[i] = j ^ i; sleep(1); for(i = 0; i < 6 * 84 / 16; ++i) pwrite(sfd, buf, 16, 0); sleep(100); } fprint(gfd, "set 26 1"); }