Pragmatics of a polyphonic calculator (chapter 2)

[Chris Chung]

The required hardware to realize this is minimal. The requirement is quite similar to a project I did a few years back. Except that It was not a calculator. It got a decent size b&w LCD (from a nokia phone), simple polyphonic tone generation via s/w + pwm. Just add a keyboard and it can be a calculator.

It runs on the same 16bit MCU as the NP-25.

The schematic for this project is as below.

Code:

//               MSP430F20x2/3       ----------o--------------o Audio out
//             -----------------     |         |              o 
//         /|\|              XIN|-   |        ---             |
//          | |                 |   .-.       --- 10-500nF    |
//          --|RST          XOUT|-  | | 1-10K  |              |
//            |                 |   |_|        |---------------
//      LED <-|P1.0             |    |        ___                               
//            |                 |    |        ///    SD / MMC card      /|\
//            |    pwm out  P2.6|-----           ---------------------   |
//            |                 |               |                Vcc 4|---
//            |    as CS    P1.7|-------------->|1 CS, select device  |
//            |    as MOSI  P1.6|<--------------|7 MISO, data out     |
//            |                 |   ----------->|2 MOSI, data in      |
//            |                 |   | --------->|5 CLK, spi clock     |
//            |                 |   | |         |                Gnd 3|---
//            |                 |   | |          ---------------------   |
//            |                 |   | |                                 ---
//            |                 |   | |           Nokia 5110 breadout   ///
//            |                 |   | |   ----------------------------- 
//            |    as SCLK  P1.1|---|-o->|7 SCLK, spi clock            |
//            |    as MISO  P1.2|---o--->|6 MOSI, data in              |
//            |    as D/C   P1.3|------->|5 D/C, data or control       |
//            |    as RST   P1.4|------->|4 RST, reset, low active     |
//            |    as SCE   P1.5|------->|3 SCE, select , low active   | /|\
//            |                 |    ----|2 Gnd                        |  |
//            |                 |    |   |                        Vcc 1|---
//                                  ---   -----------------------------
//                                  ///
//
//        SD (back side)                          Micro-SD (back side)
//        __________________                      __________________
//       /  1 2 3 4 5 6 7 8 | 1. CS      .. SEL  /  1 2 3 4 5 6 7 8 | 1. NC            
//       |9                 | 2. DATAIN  .. SDO  |                  | 2. CS      .. SEL
//       |                  | 3. GND     .. Gnd  |                  | 3. DATAIN  .. SDO
//       |  S O - + C   I   | 4. 3.3V    .. Vcc  |    S O + C - I   | 4. 3.3V    .. Vcc
//       |                  | 5. CLK     .. Clk  |                  | 5. CLK     .. Clk
//       |                  | 6. GND/NC  .. Gnd  |                  | 6. GND/NC
//       |                  | 7. DATAOUT .. SDI  |                  | 7. DATAOUT .. SDI
//       |                  | 8. DAT1            |                  | 8. DAT1
//       |                  | 9. DAT2            |                  | 9. DAT2