---
tags: [entity]
type: entity
topic: stm32-lower
note: 13
created: 2026-07-16
updated: 2026-07-16
---

# Note 13: CAN (lower/stm32/01~04)

## Projects

| # | Directory | Description | Library |
|---|---|---|---|
| 01 | `01_can_test_register` | Loopback silent mode | Register |
| 02 | `02_can_test_hal` | Loopback silent mode | HAL |
| 03 | `03_can_tx_register` | Dual-node TX | Register |
| 03 | `03_can_rx_register` | Dual-node RX | Register |
| 04 | `04_can_tx_hal` | Dual-node TX | HAL |
| 04 | `04_can_rx_hal` | Dual-node RX | HAL |

## Code Accuracy Audit

### Path Audit

| Claimed Path (in raw note) | Actual Path | Status |
|---|---|---|
| `stm32/stm32/01_can_test_register/Hardware/CAN/can.c` | `01_can_test_register/Hardware/CAN/can.c` | **WRONG** — double `stm32/` prefix |
| `stm32/stm32/01_can_test_register/User/main.c` | `01_can_test_register/User/main.c` | **WRONG** — double `stm32/` prefix |
| `stm32/02_can_test_hal/Core/Src/can.c` | `02_can_test_hal/Core/Src/can.c` | **Correct** |
| `stm32/03_can_tx_register/User/main.c` | `03_can_tx_register/User/main.c` | **Correct** (no double prefix) |
| `stm32/04_can_tx_hal/Core/Src/main.c` | `04_can_tx_hal/Core/Src/main.c` | **Correct** |

> **Critical Finding**: Raw note has `stm32/stm32/01_can_test_register/...` (duplicated `stm32/`) for project 01 files. This path does not exist. The correct base is `01_can_test_register/...` (only one level under `stm32/`).

### File Existence

| File | Exists? |
|---|---|
| `01_can_test_register/Hardware/CAN/can.c` | Yes (200 lines) |
| `01_can_test_register/Hardware/CAN/can.h` | Yes (30 lines) |
| `01_can_test_register/User/main.c` | Yes (53 lines) |
| `02_can_test_hal/Core/Src/can.c` | Yes (195 lines) |
| `02_can_test_hal/Core/Src/main.c` | Yes (219 lines) |
| `03_can_tx_register/User/main.c` | Exists |
| `03_can_rx_register/User/main.c` | Exists |
| `04_can_tx_hal/Core/Src/main.c` | Exists |
| `04_can_rx_hal/Core/Src/main.c` | Exists |

### Code Comparison: Register CAN (01_can_test_register)

| Claimed by Note | Actual Code | Match? |
|---|---|---|
| `CAN1->MCR |= CAN_MCR_INRQ` | Line 37: `CAN1->MCR |= CAN_MCR_INRQ` | ✅ Match |
| `CAN1->BTR |= CAN_BTR_SILM` and `CAN1->BTR |= CAN_BTR_LBKM` | Lines 53-54 | ✅ Match |
| `CAN1->BTR |= (35 << 0)` (BRP) | Line 59: `CAN1->BTR |= (35 << 0)` | ✅ Match |
| `CAN1->BTR |= (2 << 16)` (TS1=BS1) | Line 63 | ✅ Match |
| `CAN1->BTR |= (5 << 20)` (TS2=BS2) | Line 66 | ✅ Match |
| `CAN1->BTR |= (1 << 24)` (SJW) | Line 70 | ✅ Match |
| `CAN1->sFilterRegister[0].FR1 = 0x06e << 21` | Line 97 | ✅ Match |
| `CAN1->sFilterRegister[0].FR2 = 0x7f1 << 21` | Line 100 | ✅ Match |
| `CAN1->sTxMailBox[0].TIR |= stdID << 21` | Line 120 | ✅ Match |
| `CAN1->sTxMailBox[0].TDTR |= len << 0` | Line 130 | ✅ Match |
| CAN send: clear TDLR/TDHR then fill in loop | Lines 134-149 | ✅ Match |
| `CAN1->sTxMailBox[0].TIR |= CAN_TI0R_TXRQ` | Line 153 | ✅ Match |
| Receive: `msgCount = (CAN1->RF0R & CAN_RF0R_FMP0) >> 0` | Line 165 | ✅ Match |
| Receive: `msg->stdID = (CAN1->sFIFOMailBox[0].RIR >> 21) & 0x7ff` | Line 174 | ✅ Match |
| Receive: `msg->len = (CAN1->sFIFOMailBox[0].RDTR >> 0) & 0x0f` | Line 177 | ✅ Match |
| Receive: RDLR/RDHR extraction loop | Lines 180-195 | ✅ Match |
| `CAN1->RF0R |= CAN_RF0R_RFOM0` | Line 198 | ✅ Match |

### Code Comparison: Typedef

| Claimed by Note | Actual Code | Match? |
|---|---|---|
| `typedef struct { uint16_t stdID; uint8_t data[8]; uint8_t len; } RxMsg;` | `can.h` lines 14-19 | ✅ Match |
| `#include "stm32f10x.h"` | Line 11 | ✅ Match |

### Code Comparison: main.c (01_can_test_register)

Note claims:
- Sends 3 messages (IDs 0x066, 0x068, 0x067) with data "abcdefg", "123", "xyz" → **ACCURATE** (lines 22-32)
- Reads back from loopback using `CAN_ReceiveMsg` → **ACCURATE** (lines 35-38)
- Prints results → **ACCURATE** (lines 40-47)

### HAL CAN (02_can_test_hal)

| Claimed by Note | Actual Code (can.c) | Match? |
|---|---|---|
| `hcan.Init.Prescaler = 36` | Line 41 | ✅ Match |
| `hcan.Init.Mode = CAN_MODE_SILENT_LOOPBACK` | Line 42 | ✅ Match |
| `hcan.Init.SyncJumpWidth = CAN_SJW_2TQ` | Line 43 | ✅ Match |
| `hcan.Init.TimeSeg1 = CAN_BS1_3TQ` | Line 44 | ✅ Match |
| `hcan.Init.TimeSeg2 = CAN_BS2_6TQ` | Line 45 | ✅ Match |
| `CAN_TxHeaderTypeDef` with `StdId, IDE=CAN_ID_STD, RTR=CAN_RTR_DATA, DLC=len` | Lines 163-167 | ✅ Match |
| `HAL_CAN_AddTxMessage(&hcan, &txHeader, data, &txMailBox)` | Line 171 | ✅ Match |
| `HAL_CAN_GetRxMessage(&hcan, CAN_RX_FIFO0, &rxHeader, rxMsg[i].data)` | Line 189 | ✅ Match |
| `rxMsg[i].stdID = rxHeader.StdId; rxMsg[i].len = rxHeader.DLC` | Lines 190-191 | ✅ Match |
| Filter: 32-bit mask mode, all zeros (accept all) | Lines 126-151 | ✅ Match |

## Summary

**Overall Accuracy**: Very High (95%+)

**Issues Found**:
1. Double `stm32/stm32/` path for project 01 in raw note — does NOT exist on disk
2. All other paths are correct
3. All code snippets match actual source files exactly