uart-serial-baremetal

Name: uart-serial-baremetal
Author: mohitmishra786

141stars19forks

How to install uart-serial-baremetal?

mohitmishra786/low-level-dev-skills/uart-serial-baremetal

$npx -y skills add mohitmishra786/low-level-dev-skills --skill uart-serial-baremetal

Installs into the current project.

Summary

Bare-metal UART skill for serial console and debug. Use when configuring baud rate, polling or IRQ-driven TX/RX, or integrating DMA with UART. Activates on queries about UART bare-metal, baud BRR, serial printf, or USART interrupt.

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SKILL.md

1	# UART Serial (Bare-Metal)
2
3	## Purpose
4
5	Implement UART/USART for debug console and device communication: baud rate calculation, 8N1 framing, polling and interrupt-driven I/O, overrun handling, and optional DMA basics.
6
7	## When to Use
8
9	- First `printf`/log output on new hardware
10	- Serial protocol to sensor/module
11	- Replacing blocking HAL_UART with minimal driver
12	- Fixing garbled or missing characters
13
14	## Workflow
15
16	### 1. Baud rate (STM32)
17
18	```
19	BRR = pclk / (16 * baud) /* oversampling by 16 — check RM for USART */
20	```
21
22	```c
23	void usart2_init(uint32_t pclk, uint32_t baud) {
24	RCC->APB1ENR \|= RCC_APB1ENR_USART2EN;
25	/* GPIO PA2/PA3 AF — see gpio-baremetal */
26
27	USART2->BRR = pclk / baud; /* simplified — RM has fractional formula */
28	USART2->CR1 = USART_CR1_TE \| USART_CR1_RE \| USART_CR1_UE;
29	}
30	```
31
32	Verify `pclk` from actual clock tree (`SystemCoreClock`, APB prescaler).
33
34	### 2. Polling TX/RX
35
36	```c
37	void uart_putc(USART_TypeDef *u, char c) {
38	while (!(u->SR & USART_SR_TXE))
39	;
40	u->DR = (uint8_t)c;
41	}
42
43	char uart_getc(USART_TypeDef *u) {
44	while (!(u->SR & USART_SR_RXNE))
45	;
46	return (uint8_t)u->DR;
47	}
48	```
49
50	### 3. Interrupt-driven RX ring buffer
51
52	```c
53	void USART2_IRQHandler(void) {
54	if (USART2->SR & USART_SR_RXNE) {
55	uint8_t b = USART2->DR;
56	rb_push(&rx_rb, b);
57	}
58	if (USART2->SR & USART_SR_ORE) {
59	(void)USART2->DR; /* clear overrun — required on STM32 */
60	}
61	}
62	```
63
64	### 4. retarget `printf` (newlib)
65
66	```c
67	int _write(int fd, char *ptr, int len) {
68	(void)fd;
69	for (int i = 0; i < len; i++)
70	uart_putc(USART2, ptr[i]);
71	return len;
72	}
73	```
74
75	Link with `--specs=nosys.specs` or provide full syscalls.
76
77	### 5. Agent usage
78
79	```
80	/uart-serial-baremetal Calculate USART BRR for 115200 at 84 MHz PCLK
81	```
82
83	## Common Problems
84
85	\| Symptom \| Cause \| Fix \|
86	\|---------\|-------\|-----\|
87	\| Garbage chars \| Wrong baud/PCLK \| Recompute BRR; check APB divider \|
88	\| Lost bytes \| ORE not cleared \| Read DR on ORE; use IRQ + ringbuf \|
89	\| No output \| TX pin not AF \| GPIO alternate function \|
90	\| `printf` hangs \| `_write` missing \| Implement retarget \|
91
92	## Related Skills
93
94	- `skills/baremetal/gpio-baremetal` — TX/RX pin mux
95	- `skills/baremetal/interrupts-and-exceptions-baremetal` — USART IRQ
96	- `skills/baremetal/dma-baremetal` — UART RX DMA
97	- `skills/embedded/openocd-jtag` — semihosting alternative

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uart-serial-baremetal

141stars19forks

View on GitHub

How to install uart-serial-baremetal?

mohitmishra786/low-level-dev-skills/uart-serial-baremetal

$npx -y skills add mohitmishra786/low-level-dev-skills --skill uart-serial-baremetal

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# UART Serial (Bare-Metal)
2
3	## Purpose
4
5	Implement UART/USART for debug console and device communication: baud rate calculation, 8N1 framing, polling and interrupt-driven I/O, overrun handling, and optional DMA basics.
6
7	## When to Use
8
9	- First `printf`/log output on new hardware
10	- Serial protocol to sensor/module
11	- Replacing blocking HAL_UART with minimal driver
12	- Fixing garbled or missing characters
13
14	## Workflow
15
16	### 1. Baud rate (STM32)
17
18	```
19	BRR = pclk / (16 * baud) /* oversampling by 16 — check RM for USART */
20	```
21
22	```c
23	void usart2_init(uint32_t pclk, uint32_t baud) {
24	RCC->APB1ENR \|= RCC_APB1ENR_USART2EN;
25	/* GPIO PA2/PA3 AF — see gpio-baremetal */
26
27	USART2->BRR = pclk / baud; /* simplified — RM has fractional formula */
28	USART2->CR1 = USART_CR1_TE \| USART_CR1_RE \| USART_CR1_UE;
29	}
30	```
31
32	Verify `pclk` from actual clock tree (`SystemCoreClock`, APB prescaler).
33
34	### 2. Polling TX/RX
35
36	```c
37	void uart_putc(USART_TypeDef *u, char c) {
38	while (!(u->SR & USART_SR_TXE))
39	;
40	u->DR = (uint8_t)c;
41	}
42
43	char uart_getc(USART_TypeDef *u) {
44	while (!(u->SR & USART_SR_RXNE))
45	;
46	return (uint8_t)u->DR;
47	}
48	```
49
50	### 3. Interrupt-driven RX ring buffer
51
52	```c
53	void USART2_IRQHandler(void) {
54	if (USART2->SR & USART_SR_RXNE) {
55	uint8_t b = USART2->DR;
56	rb_push(&rx_rb, b);
57	}
58	if (USART2->SR & USART_SR_ORE) {
59	(void)USART2->DR; /* clear overrun — required on STM32 */
60	}
61	}
62	```
63
64	### 4. retarget `printf` (newlib)
65
66	```c
67	int _write(int fd, char *ptr, int len) {
68	(void)fd;
69	for (int i = 0; i < len; i++)
70	uart_putc(USART2, ptr[i]);
71	return len;
72	}
73	```
74
75	Link with `--specs=nosys.specs` or provide full syscalls.
76
77	### 5. Agent usage
78
79	```
80	/uart-serial-baremetal Calculate USART BRR for 115200 at 84 MHz PCLK
81	```
82
83	## Common Problems
84
85	\| Symptom \| Cause \| Fix \|
86	\|---------\|-------\|-----\|
87	\| Garbage chars \| Wrong baud/PCLK \| Recompute BRR; check APB divider \|
88	\| Lost bytes \| ORE not cleared \| Read DR on ORE; use IRQ + ringbuf \|
89	\| No output \| TX pin not AF \| GPIO alternate function \|
90	\| `printf` hangs \| `_write` missing \| Implement retarget \|
91
92	## Related Skills
93
94	- `skills/baremetal/gpio-baremetal` — TX/RX pin mux
95	- `skills/baremetal/interrupts-and-exceptions-baremetal` — USART IRQ
96	- `skills/baremetal/dma-baremetal` — UART RX DMA
97	- `skills/embedded/openocd-jtag` — semihosting alternative

People who liked this also viewed

6 picks

Type