Mode d’emploi
- Copiez la commande et examinez le paquet avant de l’installer dans votre environnement agent.
- Consultez le document original pour les outils, identifiants et environnements requis.
- Décrivez les entrées et le livrable souhaité ; comparez la sortie aux sources.
npx skills add https://github.com/mohitmishra786/low-level-dev-skills --skill uart-serial-baremetalAvant de commencer
- L’installation n’inclut ni abonnement au modèle, ni quota API, ni accès aux fichiers.
- Étoiles et installations reflètent l’activité, pas un test indépendant de qualité ou de sécurité.
Document Skill original
Rendu depuis le dépôt source en conservant titres, exemples, code, tableaux, liens et images.
UART Serial (Bare-Metal)
Purpose
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.
When to Use
- First
printf/log output on new hardware - Serial protocol to sensor/module
- Replacing blocking HAL_UART with minimal driver
- Fixing garbled or missing characters
Workflow
1. Baud rate (STM32)
BRR = pclk / (16 * baud) /* oversampling by 16 — check RM for USART */c
void usart2_init(uint32_t pclk, uint32_t baud) {
RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
/* GPIO PA2/PA3 AF — see gpio-baremetal */
USART2->BRR = pclk / baud; /* simplified — RM has fractional formula */
USART2->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_UE;
}Verify pclk from actual clock tree (SystemCoreClock, APB prescaler).
2. Polling TX/RX
c
void uart_putc(USART_TypeDef *u, char c) {
while (!(u->SR & USART_SR_TXE))
;
u->DR = (uint8_t)c;
}
char uart_getc(USART_TypeDef *u) {
while (!(u->SR & USART_SR_RXNE))
;
return (uint8_t)u->DR;
}3. Interrupt-driven RX ring buffer
c
void USART2_IRQHandler(void) {
if (USART2->SR & USART_SR_RXNE) {
uint8_t b = USART2->DR;
rb_push(&rx_rb, b);
}
if (USART2->SR & USART_SR_ORE) {
(void)USART2->DR; /* clear overrun — required on STM32 */
}
}4. retarget printf (newlib)
c
int _write(int fd, char *ptr, int len) {
(void)fd;
for (int i = 0; i < len; i++)
uart_putc(USART2, ptr[i]);
return len;
}Link with --specs=nosys.specs or provide full syscalls.
5. Agent usage
/uart-serial-baremetal Calculate USART BRR for 115200 at 84 MHz PCLKCommon Problems
| Symptom | Cause | Fix |
|---|---|---|
| Garbage chars | Wrong baud/PCLK | Recompute BRR; check APB divider |
| Lost bytes | ORE not cleared | Read DR on ORE; use IRQ + ringbuf |
| No output | TX pin not AF | GPIO alternate function |
printf hangs | _write missing | Implement retarget |
Related Skills
skills/baremetal/gpio-baremetal— TX/RX pin muxskills/baremetal/interrupts-and-exceptions-baremetal— USART IRQskills/baremetal/dma-baremetal— UART RX DMAskills/embedded/openocd-jtag— semihosting alternative
