UA1ZBE Custom Firmware v1.0

Features:
- VFO mode with direct frequency input
- POCSAG decoder (512/1200 baud) with BCH(31,21) correction
- Full-screen Spectrum analyzer
- FM Radio receiver
- RSSI signal indicator overlay
- Custom boot splash (UA1ZBE / POCSAG pager / build date)

Architecture:
- app/mode.c — mode dispatcher (VFO/POCSAG/Spectrum/FM)
- app/boot_splash.c — 2-second boot splash
- app/pocsag/ — POCSAG decoder + BCH correction
- app/display_rssi.c — RSSI indicator
- main.c — entry point with custom init
- syscalls.c — bare-metal _sbrk stub

Build: arm-none-eabi-gcc -Os -flto -Wall -Werror -Wextra
Size: 57.9KB Flash / 3.6KB RAM

Controls:
- 0-9: Direct frequency input (VFO)
- SK2: POCSAG mode
- SK1: Spectrum analyzer
- 0: FM Radio
- EXIT: Return to VFO
- F/*: Toggle 512/1200 baud (in POCSAG)

driver/i2c.c

@@ -0,0 +1,164 @@
+/* Copyright 2023 Dual Tachyon
+ * https://github.com/DualTachyon
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *     Unless required by applicable law or agreed to in writing, software
+ *     distributed under the License is distributed on an "AS IS" BASIS,
+ *     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *     See the License for the specific language governing permissions and
+ *     limitations under the License.
+ */
+
+#include "bsp/dp32g030/gpio.h"
+#include "bsp/dp32g030/portcon.h"
+#include "driver/gpio.h"
+#include "driver/i2c.h"
+#include "driver/systick.h"
+
+void I2C_Start(void)
+{
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	SYSTICK_DelayUs(1);
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	SYSTICK_DelayUs(1);
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+}
+
+void I2C_Stop(void)
+{
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	SYSTICK_DelayUs(1);
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	SYSTICK_DelayUs(1);
+}
+
+uint8_t I2C_Read(bool bFinal)
+{
+	uint8_t i, Data;
+
+	PORTCON_PORTA_IE |= PORTCON_PORTA_IE_A11_BITS_ENABLE;
+	PORTCON_PORTA_OD &= ~PORTCON_PORTA_OD_A11_MASK;
+	GPIOA->DIR &= ~GPIO_DIR_11_MASK;
+
+	Data = 0;
+	for (i = 0; i < 8; i++) {
+		GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+		SYSTICK_DelayUs(1);
+		GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+		SYSTICK_DelayUs(1);
+		Data <<= 1;
+		SYSTICK_DelayUs(1);
+		if (GPIO_CheckBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA)) {
+			Data |= 1U;
+		}
+		GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+		SYSTICK_DelayUs(1);
+	}
+
+	PORTCON_PORTA_IE &= ~PORTCON_PORTA_IE_A11_MASK;
+	PORTCON_PORTA_OD |= PORTCON_PORTA_OD_A11_BITS_ENABLE;
+	GPIOA->DIR |= GPIO_DIR_11_BITS_OUTPUT;
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	if (bFinal) {
+		GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	} else {
+		GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	}
+	SYSTICK_DelayUs(1);
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+
+	return Data;
+}
+
+int I2C_Write(uint8_t Data)
+{
+	uint8_t i;
+	int ret = -1;
+
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	for (i = 0; i < 8; i++) {
+		if ((Data & 0x80) == 0) {
+			GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+		} else {
+			GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+		}
+		Data <<= 1;
+		SYSTICK_DelayUs(1);
+		GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+		SYSTICK_DelayUs(1);
+		GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+		SYSTICK_DelayUs(1);
+	}
+
+	PORTCON_PORTA_IE |= PORTCON_PORTA_IE_A11_BITS_ENABLE;
+	PORTCON_PORTA_OD &= ~PORTCON_PORTA_OD_A11_MASK;
+	GPIOA->DIR &= ~GPIO_DIR_11_MASK;
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+	SYSTICK_DelayUs(1);
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+
+	for (i = 0; i < 255; i++) {
+		if (GPIO_CheckBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA) == 0) {
+			ret = 0;
+			break;
+		}
+	}
+
+	GPIO_ClearBit(&GPIOA->DATA, GPIOA_PIN_I2C_SCL);
+	SYSTICK_DelayUs(1);
+	PORTCON_PORTA_IE &= ~PORTCON_PORTA_IE_A11_MASK;
+	PORTCON_PORTA_OD |= PORTCON_PORTA_OD_A11_BITS_ENABLE;
+	GPIOA->DIR |= GPIO_DIR_11_BITS_OUTPUT;
+	GPIO_SetBit(&GPIOA->DATA, GPIOA_PIN_I2C_SDA);
+
+	return ret;
+}
+
+int I2C_ReadBuffer(void *pBuffer, uint8_t Size)
+{
+	uint8_t *pData = (uint8_t *)pBuffer;
+	uint8_t i;
+
+	for (i = 0; i < Size - 1; i++) {
+		SYSTICK_DelayUs(1);
+		pData[i] = I2C_Read(false);
+	}
+
+	SYSTICK_DelayUs(1);
+	pData[i] = I2C_Read(true);
+
+	return Size;
+}
+
+int I2C_WriteBuffer(const void *pBuffer, uint8_t Size)
+{
+	const uint8_t *pData = (const uint8_t *)pBuffer;
+	uint8_t i;
+
+	for (i = 0; i < Size; i++) {
+		if (I2C_Write(*pData++) < 0) {
+			return -1;
+		}
+	}
+
+	return 0;
+}
+