LPC bus sniffer program

Author: MrGreensWorkshop

README.md

@@ -26,6 +26,11 @@ Thank you for considering [supporting my work!](#you-can-support-my-work)
 
 I usually use old or junk parts on my projects to reduce electronic waste and support the SDGs. I was working on a project to reuse an x86-based firewall that I came across in an online auction. And I found myself reading BIOS post-codes. I thought it would be a good opportunity to talk about how the LPC bus and I/O cycles work by making a BIOS POST code reader project. So, here we are.
 
+### Features / Fixes
+
+- LPC bus sniffer
+- POST code output to USB CDC
+
 ### Compilation
 
 1. Clone the repo as shown below, or [download latest release](https://github.com/MrGreensWorkshop/RasPiPicoSDK-PicoBiosPostCodeReader/releases/latest).

src/lpc_bus_sniffer.pio

@@ -0,0 +1,88 @@
+.program lpc_bus_sniffer
+;.side_set 1 opt                 ; [DEBUG] side_set <count> (opt) (pindirs) 
+
+.define NIBBLE_LOOP_COUNT 6
+
+pull                             ; Get the filter from TX FIFO to the OSR.
+mov Y, OSR                       ; Copy OSR to Y.
+.wrap_target
+entry_point:
+mov ISR, null                    ; Clean the ISR.
+set X, (NIBBLE_LOOP_COUNT - 1)   ; Set the value to X register.
+wait 0 pin 5                     ; Wait until the LFRAME pin goes low.
+
+; Get 6 nibble (START + CY/DR + ADDR[3-0])
+read_nibble1:
+wait 0 pin 4                     ; Wait until the LCLK pin goes low.
+in pins, 4                       ; Read the LAD[0-3] pins.
+wait 1 pin 4                     ; Wait until the LCLK pin goes high.
+jmp X-- read_nibble1             ; If X is not equal to zero, decrement it and jump.
+
+; Check the frame, START + CY/DR + ADDR[0-3]
+mov X, ISR                       ; Copy ISR to X.
+jmp X!=Y entry_point             ; If X and Y registers are not equal jump.
+
+; Get 1 nibble (DATA[0])
+wait 0 pin 4                     ; Wait until the LCLK pin goes low.
+in pins, 4                       ; Get the DATA[0].
+wait 1 pin 4                     ; Wait until the LCLK pin goes high.
+
+; Get 1 nibble (DATA[1])
+wait 0 pin 4                     ; Wait until the LCLK pin goes low.
+in pins, 4                       ; Get the DATA[1].
+wait 1 pin 4                     ; Wait until the LCLK pin goes high.
+
+in null, 24                      ; Shift the ISR 24 bit to get DATA.
+push                             ; Push to get the DATA value on terminal.
+.wrap
+
+% c-sdk {
+
+//#define SIDE_PIN 26   // For debugging
+
+void lpc_bus_sniffer_program_init(PIO pio, uint sm, uint offset, uint lpc_bus_pin_base) {
+   pio_sm_config c = lpc_bus_sniffer_program_get_default_config(offset);
+
+   // Connect the GPIOs to selected PIO block
+   for(uint i = lpc_bus_pin_base; i < lpc_bus_pin_base + 6; i++) {
+      pio_gpio_init(pio, i);
+   }
+
+#ifdef SIDE_PIN
+   pio_gpio_init(pio, SIDE_PIN);
+#endif
+
+   // Set the selected pin directions for the selected 6 pins. LAD[0-3] + LCLK + LFRAME (false: in)
+   pio_sm_set_consecutive_pindirs(pio, sm, lpc_bus_pin_base, 6, false);
+
+#ifdef SIDE_PIN
+   // Set the selected pin direction for the selected 1 pin. SIDE_PIN (true: out)
+   pio_sm_set_consecutive_pindirs(pio, sm, SIDE_PIN, 1, true );
+#endif
+
+   sm_config_set_in_shift(
+      &c,
+      true,  // ShiftDir : true: shift ISR to right, false: shift ISR to left
+      false, // AutoPush : true: enabled, false: disabled
+      0      // AutoPush threshold: <0-32>
+   );
+
+   sm_config_set_out_shift(
+      &c,
+      true,  // ShiftDir : true: shift OSR to right, false: shift OSR to left
+      false, // AutoPull : true: enabled, false: disabled
+      0      // AutoPull threshold: <0-32>
+   );
+
+   // Set 'IN' base pin. To read the LAD[0-3].
+   sm_config_set_in_pins(&c, lpc_bus_pin_base);
+
+#ifdef SIDE_PIN
+   // Set 'SIDESET' base pin. It's for debugging.
+   sm_config_set_sideset_pins(&c, SIDE_PIN);
+#endif
+
+   pio_sm_init(pio, sm, offset, &c);
+}
+
+%}

src/main.c

@@ -3,6 +3,10 @@
 #include "pico/stdlib.h"
 #include "hardware/pio.h"
 #include "hardware/clocks.h"
+#include "lpc_bus_sniffer.pio.h"
+
+// Set the system frequency to 33 MHz x 6 to make time for handling LPC frames.
+#define SYS_FREQ_IN_KHZ (198 * 1000)
 
 #define LED_STATUS_PIN PICO_DEFAULT_LED_PIN
 #define INTERVAL_IM_ALIVE_MS (1000)
@@ -23,6 +27,37 @@ void flash_led_once(void) {
     gpio_put(LED_STATUS_PIN, 0);
 }
 
+int init_lpc_bus_sniffer(PIO pio) {
+    // LAD[0-3] + LCLK + LFRAME which starts from GPIO0
+    uint lpc_bus_pin_base = 0;
+    uint offset;
+
+    printf("initializing the lpc bus sniffer program\n");
+
+    int sm = pio_claim_unused_sm(pio, true);
+    if(sm < 0){
+        printf("Error: Cannot claim a free state machine\n");
+        return -1;
+    }
+
+    if (pio_can_add_program(pio, &lpc_bus_sniffer_program)) {
+        offset = pio_add_program(pio, &lpc_bus_sniffer_program);
+    } else {
+        printf("Error: pio program can not be loaded\n");
+        return -2;
+    }
+
+    lpc_bus_sniffer_program_init(pio, sm, offset, lpc_bus_pin_base);
+    pio_sm_set_enabled(pio, sm, true);
+
+    // To sniff the POST codes
+    // Set the filter to I/O write cycle (0x2) and the address to 0x80.
+    pio->txf[sm] = 0x08002000;
+
+    printf("program loaded at %d, sm: %d\n", offset, sm);
+    return sm;
+}
+
 bool repeating_timer_callback(struct repeating_timer *t) {
     // Print the I'm alive sign every 1 sec.
     printf("...\n");
@@ -33,11 +68,19 @@ int main() {
     // Initialize the GPIOs. 
     gpio_initialization();
 
+    // Set the system frequency.
+    set_sys_clock_khz(SYS_FREQ_IN_KHZ, true);
+
     stdio_init_all();
     // Wait for a while. Otherwise, USB CDC doesn't print all printfs.
     sleep_ms(500);
     printf("STARTED\n");
 
+    // Init the PIO
+    PIO _pio0 = pio0;
+    int sm_lpc_bus_sniffer = init_lpc_bus_sniffer(_pio0);
+    if (sm_lpc_bus_sniffer < 0) return -1;
+
     // Print the  system frequency.
     printf("System clock is %u kHz\n", frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_SYS));
 
@@ -51,5 +94,10 @@ int main() {
     flash_led_once();
     printf("Starting to sample the POST codes.\n");
 
-    while(1);
+    while(1) {
+        if (!pio_sm_is_rx_fifo_empty(_pio0, sm_lpc_bus_sniffer)) {
+            uint32_t rxdata = _pio0->rxf[sm_lpc_bus_sniffer];
+            printf("data: %02x\n", rxdata);
+        }
+    }
 }