Commit old working changes

2026-08-07 01:13:18 +00:00 · 2024-08-23 12:26:42 -07:00
parent b9382b26d7
commit 977041bd67
7 changed files with 1105 additions and 16 deletions
@@ -0,0 +1,85 @@
+#include <avr/io.h>
+#include <avr/sfr_defs.h>
+
+// char AC0_STATUS_STATE_bm = (1<<4);
+
+#define MAXMSGLEN 32
+
+uint8_t message[32];
+uint8_t current_uint8_t;
+uint8_t nbits;
+
+typedef struct AVCLAN_frame_struct {
+  uint16_t sender_addr;   // formerly "master"
+  uint16_t receiver_addr; // formerly "slave"
+  uint8_t control;
+  uint8_t length;
+  uint8_t data[MAXMSGLEN];
+} AVCLAN_frame_t;
+
+int8_t AVCLAN_read_data(uint8_t *data, uint8_t nbits) {
+  int8_t parity = 0;
+  uint8_t bits = 0;
+  while (bits < nbits) {
+    loop_until_bit_is_set(TCB0.INTFLAGS, 0);
+    uint16_t period = TCB0.CNT;
+    uint16_t pulse = TCB0.CCMP;
+    if ((period - pulse) < 0x033) {
+      (*data)++;
+      parity++;
+    }
+    bits++;
+    if ((bits ^ 0x08) == 1) {
+      data++;
+    }
+  }
+  return parity;
+}
+
+int8_t AVCLAN_read_data_asm(uint8_t *data, uint8_t nbits) {
+  int8_t parity = 0;
+  uint8_t bits = 0;
+  uint8_t uint8_t = data[0];
+  while (bits < nbits) {
+    loop_until_bit_is_set(TCB0.INTFLAGS, 0);
+    __asm__ __volatile__(
+        "sub  %A[tcb],%C[tcb]       ; TCB0_CNT - TCB0_CCMP (low) \n\t"
+        "sbc  %B[tcb],%D[tcb]       ; TCB0_CNT - TCB0_CCMP (high) \n\t"
+        "cp   %A[tcb],lo8(thresh)   ; Compare low \n\t"
+        "cpc  %B[tcb],hi8(thresh)   ; Compare high; carry flag is set if "
+        "(TCB_CNT - TCB_CCMP) < half_per (ie read bit is 0x01)\n\t"
+        "brcc skipparity            ; Skip incrementing parity if bit was 0 "
+        "\n\t"
+        "inc  %[parity]             ; Increment parity (doesn't change carry "
+        "flag) \n"
+        "skipparity:                     \n\t"
+        "rol  %[data]               ; Rotate left with carry flag \n\t"
+        "inc  %[bits]               ; Increment \n\t"
+        "mov  __tmp_reg__,%[bits]    ; Copy to temp registry to avoid messing "
+        "with loop count \n\t"
+        "eor  __tmp_reg__,$0x09      ; Reset if greater than 8 \n\t"
+        "brbc 1,end                  ; The current uint8_t read was just "
+        "completed; increment the pointer \n\t"
+        "std  %a[data_ADDR]+,%[data] ; \n"
+        "end:                            \n\t"
+        : [data_ADDR] "+e"(data), [bits] "+r"(bits), [parity] "+r"(parity)
+        : [tcb] "r"(_SFR_MEM32(
+              &TCB0_CNT)), // TCB0_CNT and TCB0_CCMP are consecutive uint16_t.
+                           // Load address of TCB0_CNT and access both words
+                           // using offsets from that pointer
+          [data] "r"(uint8_t),
+          [thresh] "M"(0x0033) // Length of synchronization period (~20us) plus
+                               // fudge factor to distinguish `0` (~20us +
+                               // ~13us) from `1` (~20us)
+        : "memory");
+  }
+  return parity;
+}
+
+int main() {
+  uint8_t message[2];
+  uint16_t master;
+
+  int8_t parity = AVCLAN_read_data((uint8_t *)(&message), 16);
+  parity = AVCLAN_read_data_asm((uint8_t *)(&master), 12);
+}