Add paracli, a parallel port comm utility

2025-09-29 18:00:55 +02:00
parent 83e267fa36
commit 8b434f4434
5 changed files with 251 additions and 1 deletions
--- a/paracomm.c
+++ b/paracomm.c
@@ -0,0 +1,127 @@
+#include "paracomm.h"
+
+#include <stdlib.h>
+
+#define kMosiIdleByte 0x00
+#define kMosiStartByte 0x42
+#define kMisoIdleNibble 0x0
+#define kMisoStartNibble 0xa
+
+static uint8_t mosi_workbuf[2][256];
+static uint8_t mosi_workbuf_idx;
+static uint8_t mosi_workbuf_size;
+
+static uint8_t* mosi_sendbuf;
+static uint8_t mosi_size;
+static uint8_t mosi_sent;
+
+static uint8_t mosi_state;
+
+static uint8_t miso_recvbuf[256];
+static uint8_t miso_size;
+static uint8_t miso_received_nibbles;
+static uint8_t miso_state;
+static void (*miso_cb)(const uint8_t*, uint8_t);
+
+static void swapbuffers() {
+    mosi_sendbuf = mosi_workbuf[mosi_workbuf_idx];
+    mosi_size = mosi_workbuf_size;
+
+    mosi_workbuf_size = 0;
+    mosi_workbuf_idx = (mosi_workbuf_idx + 1) % 2;
+}
+
+uint8_t paracomm_nextbyte() {
+    switch (mosi_state) {
+        case 0:
+            if (mosi_size == 0) {
+                swapbuffers();
+                if (mosi_size == 0) {
+                    return kMosiIdleByte;
+                }
+            }
+            mosi_state = 1;
+            return kMosiStartByte;
+        case 1:
+            // assert(mosi_size > 0)
+            mosi_sent = 0;
+            mosi_state = 2;
+            return mosi_size;
+        case 2:
+            {
+                uint8_t b = mosi_sendbuf[mosi_sent];
+                mosi_sent += 1;
+
+                if (mosi_sent == mosi_size) {
+                    swapbuffers();
+                    mosi_state = 0;
+                }
+
+                return b;
+            }
+    }
+
+    __builtin_unreachable();
+}
+
+void paracomm_feed(uint8_t n) {
+    switch (miso_state) {
+        case 0:
+            if (n == kMisoStartNibble) {
+                miso_state = 1;
+            } else if (n == kMisoIdleNibble) {
+            } else {
+                // error: spurious nibble
+            }
+            break;
+        case 1:
+            miso_size = n;
+            miso_state = 2;
+            break;
+        case 2:
+            miso_size += n << 4;
+            miso_received_nibbles = 0;
+            miso_state = 3;
+            break;
+        case 3:
+            {
+                uint8_t idx = miso_received_nibbles / 2;
+                if (miso_received_nibbles % 2 == 0) {
+                    miso_recvbuf[idx] = n;
+                } else {
+                    miso_recvbuf[idx] += n << 4;
+                }
+                miso_received_nibbles += 1;
+
+                if (miso_received_nibbles == 2*miso_size) {
+                    if (miso_cb != 0) {
+                        miso_cb(miso_recvbuf, miso_size);
+                    }
+                    miso_state = 0;
+                }
+            }
+            break;
+    }
+}
+
+void paracomm_init(miso_cb_t cb) {
+    mosi_size = 0;
+    mosi_workbuf_idx = 0;
+    mosi_workbuf_size = 0;
+    mosi_state = 0;
+
+    miso_state = 0;
+    miso_cb = cb;
+}
+
+int paracomm_send(uint8_t b) {
+    if (mosi_workbuf_size == 256) {
+        return -1;
+    }
+
+    uint8_t* buff = mosi_workbuf[mosi_workbuf_idx];
+    buff[mosi_workbuf_size] = b;
+    mosi_workbuf_size += 1;
+
+    return 0;
+}