Diff: example3.h

Revision:

0:055897ab699b

Child:

1:46c8c60e744a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/example3.h	Sun Jan 16 18:27:44 2011 +0000
@@ -0,0 +1,153 @@
+/*
+    Copyright (c) 2011 Andy Kirkham
+ 
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+ 
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+ 
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+*/
+
+#ifdef MAX3100_EXAMPLE_COMPILE
+
+/*
+ * NOTE! Unlike examples 1 & 2 (which are tested in the real world) this example
+ * is theoretical only as I have not tested it. It should work but if you try it 
+ * and it doesn't work let me know! It's shown here as a starting point to demo
+ * how to share multiple MAX3100 interrupts and address multiple chips using
+ * external hardware to manage each MAX3100's CS signal.
+ * 
+ * Connecting up the MAX3100 for this test program. Note, to form a "loopback"
+ * the MAX3100 TX pin (13) is connected to the RX pin (12). Don't forget thwe Xtal
+ * and power pins that are not shown here. Although I do PullUp mode on the IRQ pin
+ * I still needed a real external pull up resistor on the IRQ line. You may need one
+ * also.
+ *
+ *                      __________
+ *                     /          \
+ *      Mbed p8 |---> 1| A0    Y0 | 15 -----> MAX0
+ *           p9 |---> 2| A1    Y1 | 14 -----> MAX1
+ *          p10 |---> 3| A2    Y2 | 13 -----> MAX2
+ *          p11 |---> 5| CS3   Y3 | 12 -----> MAX3 (and on to MAX7)
+ *                     \__________/ TTL138 (Tie CS1 to +ve and CS2 to 0v)
+ *
+ *                                          ____________
+ *                                         /            \ U1
+ * Mbed MOSI p5 |-------*---------------> 1| Din     TX | 13 ------\
+ *      MISO p6 |-----*-|---------------> 2| Dout       |          |
+ *      SCLK p7 |---*-|-|---------------> 3| Sclk    RX | 12 ------/
+ *                  | | |        MAX0 --> 4| CS         |
+ *          p12 |-*-|-|-|---------------> 5| IRQ        | MAX3100 
+ *                | | | |        +5v ---> 6| SHTD       | Xtal and PWR not shown.
+ *                | | | |                  \____________/
+ *                | | | |                   ____________
+ *                | | | |                  /            \ U2
+ *                | | | *---------------> 1| Din     TX | 13 ------\
+ *                | | *-|---------------> 2| Dout       |          |
+ *                | *-|-|---------------> 3| Sclk    RX | 12 ------/
+ *                | | | |        MAX1 --> 4| CS         |
+ *                *-|-|-|---------------> 5| IRQ        | MAX3100
+ *                | | | |        +5v ---> 6| SHTD       | Xtal and PWR not shown.
+ *                | | | |                  \____________/
+ *                | | | |                   ____________
+ *                | | | |                  /            \ U3
+ *                | | | \---------------> 1| Din     TX | 13 ------\
+ *                | | \-----------------> 2| Dout       |          |
+ *                | \-------------------> 3| Sclk    RX | 12 ------/
+ *                |              MAX2 --> 4| CS         |
+ *                \---------------------> 5| IRQ        | MAX3100
+ *                               +5v ---> 6| SHTD       | Xtal and PWR not shown.
+ *                                         \____________/
+ *
+ * Assume a further 5 MAX3100 devices connected to the bus in the same way
+ * to make a total of 8 MAX3100 serial devices connected to a single SPI bus.
+ * Additionally, they all share the same interrupt signal. This is possible 
+ * because the MAX3100 IRQ output is open drain. So you will need an external 1k
+ * pull up resistor on the IRQ signal.
+ */
+
+#include "mbed.h"
+#include "MAX3100.h"
+
+Serial       pc(USBTX, USBRX);
+SPI          spi(p5, p6, p7);
+BusOut       addr(p8, p9, p10);
+DigitalOut   cs(p11);
+InterruptIn  irq(p12);
+MAX3100      *max[8];
+
+// Class used to decode the address and handle shared interrupts.
+class MAX3100_Addr {
+public:
+    void cs_select(int device, int val) { 
+        addr = device & 0x7; // Select device.
+        cs.write(val & 1);   // Assert/deassert chip CS.
+    }
+    void isr(void) {
+        for (int i = 0; i < 8; i++) {
+            if (max[i] != (MAX3100 *)NULL) max[i]->isr();
+        }
+    }
+};
+
+MAX3100_Addr address;
+
+int main() {
+    int index;
+    
+    cs = 1;
+    
+    // Set the PC USB serial baud rate.
+    pc.baud(115200);
+
+    // Format the SPI interface.    
+    spi.format(16, 0);
+    spi.frequency(MAX3100_SPI_FREQ);
+    
+    // Create the 8 devices and set them up.
+    for (int index = 0; index < 8; index++) {
+        max[index] = new MAX3100(&spi, NC, NC);  
+        max[index]->setDevice(index);   
+        max[index]->enableRxIrq();
+        max[index]->enableTxIrq();
+        max[index]->attach_cs(&address, &MAX3100_Addr::cs_select);
+    }
+    
+    // Connect the interrupt signal.
+    irq.fall(&address, &MAX3100_Addr::isr);
+    
+    // Any byte received on the "USB serial port" is sent to all MAX3100 devices.
+    // Any byte received by a MAX3100 device is sent to the "USB serial port".
+    while (1) {
+        if (pc.readable()) {
+            int c = pc.getc();
+            for (index = 0; index < 8; index++) {
+                if (max[index] != (MAX3100 *)NULL) {
+                    while (!max[index]->writable());
+                    max[index]->putc(c);            
+                }
+            }            
+        }
+        for (index = 0; index < 8; index++) {
+            if (max[index] != (MAX3100 *)NULL) {
+                if (max[index]->readable()) {
+                    pc.putc(max[index]->getc());
+                }    
+            }
+        }        
+    }    
+}
+
+#endif