libftdi: (tomj) short CBUS mode example

diff --git a/examples/bitbang_cbus.c b/examples/bitbang_cbus.c
new file mode 100644 (file)
index 0000000..6163af8
--- /dev/null
+++ b/examples/bitbang_cbus.c
@@ -0,0 +1,78 @@
+/*  bitbang_cbus.c
+
+    Example to use CBUS bitbang mode of newer chipsets.
+    You must enable CBUS bitbang mode in the EEPROM first.
+
+    Thanks to Steve Brown <sbrown@ewol.com> for the
+    the information how to do it.
+
+    The top nibble controls input/output and the bottom nibble
+    controls the state of the lines set to output. The datasheet isn't clear
+    what happens if you set a bit in the output register when that line is
+    conditioned for input. This is described in more detail
+    in the FT232R bitbang app note.
+
+    BITMASK
+    CBUS Bits
+    3210 3210
+    xxxx xxxx
+    |    |------ Output Control 0->LO, 1->HI
+    |----------- Input/Output   0->Input, 1->Output
+
+    Example:
+    All pins to output with 0 bit high: 0xF1 (11110001)
+    Bits 0 and 1 to input, 2 and 3 to output and masked high: 0xCC (11001100)
+
+    This program is distributed under the GPL, version 2
+*/
+
+#include <stdio.h>
+#include <unistd.h>
+#include <ftdi.h>
+
+int main(int argc, char **argv)
+{
+    struct ftdi_context ftdic;
+    int f,i;
+    char buf[1];
+    unsigned char bitmask;
+
+    ftdi_init(&ftdic);
+
+    f = ftdi_usb_open(&ftdic, 0x0403, 0x6001);
+    if(f < 0 && f != -5) {
+        fprintf(stderr, "unable to open ftdi device: %d (%s)\n", f, ftdi_get_error_string(&ftdic));
+        exit(-1);
+    }
+    printf("ftdi open succeeded: %d\n",f);
+
+    // enable CBUS
+    bitmask = 0x71;
+    printf("enabling CBUS mode\n");
+    f = ftdi_set_bitmode(&ftdic, bitmask, 0x20); // cbus[0] as input (high), cbus[1-3] as output
+    if (f < 0) {
+        fprintf(stderr, "set_bitmode failed for 0x%x, error %d (%s)\n", bitmask, f, ftdi_get_error_string(&ftdic));
+        exit(-1);
+    }
+
+    // write to CBUS
+    buf[0] = 0xFF;
+    f = ftdi_write_data(&ftdic, buf, 1);
+    if(f < 0) {
+        fprintf(stderr,"write failed for 0x%x, error %d (%s)\n", buf[0], f, ftdi_get_error_string(&ftdic));
+        exit(-1);
+    }
+
+    // read CBUS
+    f = ftdi_read_pins(&ftdic, &buf[0]);
+    if (f < 0) {
+        fprintf(stderr, "read_pins failed, error %d (%s)\n", f, ftdi_get_error_string(&ftdic));
+        exit(-1);
+    }
+
+    printf("disabling bitbang mode\n");
+    ftdi_disable_bitbang(&ftdic);
+
+    ftdi_usb_close(&ftdic);
+    ftdi_deinit(&ftdic);
+}