echoplayer: implement ADC to read battery voltage

commit acd3a5f0cefed9b6f6edb85584d54f104d8de961
Author: Aidan MacDonald <[email protected]>
Date:   Wed Mar 18 12:42:18 2026 +0000

    echoplayer: implement ADC to read battery voltage
    
    Change-Id: I8043e7d2f02c10cb8c9d9ec59b7d216945431481

diff --git a/firmware/SOURCES b/firmware/SOURCES
index ca90c2f3d7..14365f965e 100644
--- a/firmware/SOURCES
+++ b/firmware/SOURCES
@@ -1926,7 +1926,6 @@ target/arm/rk27xx/ihifi2/audio-ihifi800.c
 #if CONFIG_CPU == STM32H743
 target/arm/stm32/crt0-stm32h7.S
 target/arm/stm32/vectors-stm32h7.S
-target/arm/stm32/adc-stm32h7.c
 #ifndef BOOTLOADER
 target/arm/stm32/debug-stm32h7.c
 #endif
@@ -1942,6 +1941,7 @@ target/arm/stm32/usb-stm32h7.c
 #endif
 
 #if defined(ECHO_R1)
+target/arm/stm32/echoplayer/adc-echoplayer.c
 target/arm/stm32/echoplayer/audiohw-echoplayer.c
 target/arm/stm32/echoplayer/backlight-echoplayer.c
 target/arm/stm32/echoplayer/button-echoplayer.c
diff --git a/firmware/reggen/stm32h743.regs b/firmware/reggen/stm32h743.regs
index 7dc6153c2c..03292c347c 100644
--- a/firmware/reggen/stm32h743.regs
+++ b/firmware/reggen/stm32h743.regs
@@ -1509,3 +1509,251 @@ I2C1 @ 0x40005400 : I2C
 I2C2 @ 0x40005800 : I2C
 I2C3 @ 0x40005C00 : I2C
 I2C4 @ 0x58001C00 : I2C
+
+block ADC {
+    ISR @ 0x00 : reg {
+        12 LDORDY
+        10 JQOVF
+        09 AWD3
+        08 AWD2
+        07 AWD1
+        06 JEOS
+        05 JEOC
+        04 OVR
+        03 EOS
+        02 EOC
+        01 EOSMP
+        00 ADRDY
+    }
+
+    IER @ 0x04 : reg {
+        10 JQOVFIE
+        09 AWD3IE
+        08 AWD2IE
+        07 AWD1IE
+        06 JEOSIE
+        05 JEOCIE
+        04 OVRIE
+        03 EOSIE
+        02 EOCIE
+        01 EOSMPIE
+        00 ADRDYIE
+    }
+
+    CR @ 0x08 : reg {
+        -- 31 ADCAL
+        -- 30 ADCALDIF
+        -- 29 DEEPPWD
+        -- 28 ADVREGEN
+        -- 27 LINCALRDYW6
+        -- 26 LINCALRDYW5
+        -- 25 LINCALRDYW4
+        -- 24 LINCALRDYW3
+        -- 23 LINCALRDYW2
+        -- 22 LINCALRDYW1
+        -- 16 ADCALLIN
+        -- 09 BOOST1 // present on revision V only
+        -- 08 BOOST0
+        -- 05 JADSTP
+        -- 04 ADSTP
+        -- 03 JADSTART
+        -- 02 ADSTART
+        -- 01 ADDIS
+        -- 00 ADEN
+    }
+
+    CFGR @ 0x0c : reg {
+        -- 31 JQDIS
+        30 26 AWD1CH
+        -- 25 JAUTO
+        -- 24 JAWD1EN
+        -- 23 AWD1EN
+        -- 22 AWD1SGL
+        -- 21 JQM
+        -- 20 JDISCEN
+        19 17 DISCNUM
+        -- 16 DISCEN
+        -- 14 AUTDLY
+        -- 13 CONT
+        -- 12 OVRMOD
+        11 10 EXTEN
+        09 05 EXTSEL
+        04 02 RES
+        01 00 DMNGT
+    }
+
+    CFGR2 @ 0x10 : reg {
+        31 28 LSHIFT
+        25 16 OSVR
+        -- 14 RSHIFT4
+        -- 13 RSHIFT3
+        -- 12 RSHIFT2
+        -- 11 RSHIFT1
+        -- 10 ROVSM
+        -- 09 TROVS
+        08 05 OVSS
+        -- 01 JOVSE
+        -- 00 ROVSE
+    }
+
+    enum SMPTIME {
+        0 = 1_5CYCLE
+        1 = 2_5CYCLE
+        2 = 8_5CYCLE
+        3 = 16_5CYCLE
+        4 = 32_5CYCLE
+        5 = 64_5CYCLE
+        6 = 387_5CYCLE
+        7 = 810_5CYCLE
+    }
+
+    SMPR1 @ 0x14 : reg {
+        29 27 SMP9 : SMPTIME
+        26 24 SMP8 : SMPTIME
+        23 21 SMP7 : SMPTIME
+        20 18 SMP6 : SMPTIME
+        17 15 SMP5 : SMPTIME
+        14 12 SMP4 : SMPTIME
+        11 09 SMP3 : SMPTIME
+        08 06 SMP2 : SMPTIME
+        05 03 SMP1 : SMPTIME
+        02 00 SMP0 : SMPTIME
+    }
+
+    SMPR2 @ 0x18 : reg {
+        29 27 SMP19 : SMPTIME
+        26 24 SMP18 : SMPTIME
+        23 21 SMP17 : SMPTIME
+        20 18 SMP16 : SMPTIME
+        17 15 SMP15 : SMPTIME
+        14 12 SMP14 : SMPTIME
+        11 09 SMP13 : SMPTIME
+        08 06 SMP12 : SMPTIME
+        05 03 SMP11 : SMPTIME
+        02 00 SMP10 : SMPTIME
+    }
+
+    PCSEL @ 0x1c : reg
+    LTR1 @ 0x20 : reg
+    HTR1 @ 0x24 : reg
+
+    SQR1 @ 0x30 : reg {
+        28 24 SQ4
+        22 18 SQ3
+        16 12 SQ2
+        10 06 SQ1
+        03 00 L
+    }
+
+    SQR2 @ 0x34 : reg {
+        28 24 SQ9
+        22 18 SQ8
+        16 12 SQ7
+        10 06 SQ6
+        04 00 SQ5
+    }
+
+    SQR3 @ 0x38 : reg {
+        28 24 SQ14
+        22 18 SQ13
+        16 12 SQ12
+        10 06 SQ11
+        04 00 SQ10
+    }
+
+    SQR4 @ 0x38 : reg {
+        10 06 SQ16
+        04 00 SQ15
+    }
+
+    DR @ 0x40 : reg
+
+    JSQR @ 0x4c : reg {
+        31 27 JSQ4
+        25 21 JSQ3
+        19 15 JSQ2
+        13 09 JSQ1
+        08 07 JEXTEN
+        06 02 JEXTSEL
+        01 00 JL
+    }
+
+    OFR @ 0x60 [4; 0x04] : reg {
+        -- 31 SSATE
+        30 26 OFFSET_CH
+        25 00 OFFSET
+    }
+
+    JDR @ 0x80 [4; 0x04] : reg
+
+    AWD2CR @ 0xa0 : reg {
+        19 00 AWD2CH
+    }
+
+    AWD3CR @ 0xa4 : reg {
+        19 00 AWD3CH
+    }
+
+    LTR2 @ 0xb0 : reg
+    HTR2 @ 0xb4 : reg
+    LTR3 @ 0xb8 : reg
+    HTR3 @ 0xbc : reg
+
+    DIFSEL @ 0xc0 : reg
+
+    CALFACT @ 0xc4 : reg {
+        26 16 D
+        10 00 S
+    }
+
+    CALFACT2 @ 0xc8 : reg {
+        29 00 LINCALFACT
+    }
+
+    CSR @ 0x300 : reg {
+        26 JQOVF_SLV
+        25 AWD3_SLV
+        24 AWD2_SLV
+        23 AWD1_SLV
+        22 JEOS_SLV
+        21 JEOC_SLV
+        20 OVR_SLV
+        19 EOS_SLV
+        18 EOC_SLV
+        17 EOSMP_SLV
+        16 ADRDY_SLV
+        10 JQOVF_MST
+        09 AWD3_MST
+        08 AWD2_MST
+        07 AWD1_MST
+        06 JEOS_MST
+        05 JEOC_MST
+        04 OVR_MST
+        03 EOS_MST
+        02 EOC_MST
+        01 EOSMP_MST
+        00 ADRDY_MST
+    }
+
+    CCR @ 0x308 : reg {
+        -- 24 VBATEN
+        -- 23 TSEN
+        -- 22 VREFEN
+        21 18 PRESC
+        17 16 CKMOD
+        15 14 DAMDF
+        10 08 DELAY
+        04 00 DUAL
+    }
+
+    CDR @ 0x30c : reg {
+        31 16 RDATA_SLV
+        15 00 RDATA_MST
+    }
+
+    CDR2 @ 0x310 : reg
+}
+
+ADC1 @ 0x40022000 : ADC
+ADC2 @ 0x40022100 : ADC
+ADC3 @ 0x58026000 : ADC
diff --git a/firmware/target/arm/stm32/adc-stm32h7.c b/firmware/target/arm/stm32/adc-stm32h7.c
deleted file mode 100644
index 8d53ba8e1f..0000000000
--- a/firmware/target/arm/stm32/adc-stm32h7.c
+++ /dev/null
@@ -1,25 +0,0 @@
-/***************************************************************************
- *             __________               __   ___.
- *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
- *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
- *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
- *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
- *                     \/            \/     \/    \/            \/
- * $Id$
- *
- * Copyright (C) 2025 by Aidan MacDonald
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
- * KIND, either express or implied.
- *
- ****************************************************************************/
-#include "adc.h"
-
-void adc_init(void)
-{
-}
diff --git a/firmware/target/arm/stm32/echoplayer/adc-echoplayer.c b/firmware/target/arm/stm32/echoplayer/adc-echoplayer.c
new file mode 100644
index 0000000000..245f0375db
--- /dev/null
+++ b/firmware/target/arm/stm32/echoplayer/adc-echoplayer.c
@@ -0,0 +1,140 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2026 by Aidan MacDonald
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "adc.h"
+#include "mutex.h"
+#include "kernel.h"
+#include "fixedpoint.h"
+#include "regs/stm32h743/adc.h"
+#include "regs/stm32h743/rcc.h"
+
+#define VREF_MV 3300
+
+static volatile void *const adc3 = (void *)ITA_ADC3;
+static struct mutex adc_mutex;
+
+static void set_smptime(volatile void *adcbase, int channel, uint32_t smpval)
+{
+    uint32_t reg_off = ITO_ADC_SMPR1;
+    if (channel > 10)
+    {
+        reg_off = ITO_ADC_SMPR2;
+        channel -= 10;
+    }
+
+    volatile uint32_t *reg = adcbase + reg_off;
+    uint32_t reg_val = *reg;
+
+    reg_val &= ~(0x7 << (channel * 3));
+    reg_val |= smpval << (channel * 3);
+
+    *reg = reg_val;
+}
+
+void adc_init(void)
+{
+    mutex_init(&adc_mutex);
+    reg_writef(RCC_AHB4ENR, ADC3EN(1));
+
+    /* Power up ADC */
+    reg_writelf(adc3, ADC_CR, DEEPPWD(0));
+    reg_writelf(adc3, ADC_CR, ADVREGEN(1));
+    while (!reg_readlf(adc3, ADC_ISR, LDORDY));
+
+    /* Run calibration */
+    reg_writelf(adc3, ADC_CR, ADCALDIF(0), ADCALLIN(1), ADCAL(1));
+    while (reg_readlf(adc3, ADC_CR, ADCAL));
+
+    /* Enable the ADC */
+    reg_assignlf(adc3, ADC_ISR, ADRDY(1));
+    reg_writelf(adc3, ADC_CR, ADEN(1));
+    while (!reg_readlf(adc3, ADC_ISR, ADRDY));
+
+    /* Set sampling times for each channel (387.5 cycles @ 6 MHz = 64.5us) */
+    set_smptime(adc3, ADC_CHANNEL_VBUS,    BV_ADC_SMPR1_SMP0_387_5CYCLE);
+    set_smptime(adc3, ADC_CHANNEL_BATTERY, BV_ADC_SMPR1_SMP0_387_5CYCLE);
+}
+
+/*
+ * Converts raw ADC reading to millivolts, assuming the
+ * ADC samples the output of a voltage divider as in the
+ * following circuit:
+ *
+ *      [VIN]---[R1]
+ *                |
+ *                +----[ADC]
+ *                |
+ *              [R2]
+ *                |
+ *              [GND]
+ *
+ * The value returned is the voltage at the VIN node.
+ */
+static uint32_t scale_adc_val(uint32_t raw_val,
+                              uint32_t vref_mV,
+                              uint32_t r1_ohms,
+                              uint32_t r2_ohms)
+{
+    /*
+     * Finds the best fracbits value which doesn't overflow.
+     * GCC will optimize this loop to a constant.
+     */
+    uint32_t fracbits = 16;
+    uint32_t conv_fac;
+    for (; fracbits > 0; --fracbits)
+    {
+        conv_fac = fp_div(r1_ohms + r2_ohms, r2_ohms, fracbits);
+        if (conv_fac <= UINT16_MAX)
+            break;
+    }
+
+    uint32_t conv_val = fp_mul(raw_val, conv_fac, fracbits);
+    return fp_mul(vref_mV, conv_val, 16);
+}
+
+unsigned short adc_read(int channel)
+{
+    mutex_lock(&adc_mutex);
+
+    /* Configure ADC to read the channel */
+    reg_writelf(adc3, ADC_SQR1, L(1 - 1), SQ1(channel));
+    reg_varl(adc3, ADC_PCSEL) = (1 << channel);
+
+    /* Start conversion & wait until complete */
+    reg_writelf(adc3, ADC_CR, ADSTART(1));
+    while (reg_readlf(adc3, ADC_CR, ADSTART));
+
+    uint32_t raw_val = reg_readl(adc3, ADC_DR);
+
+    mutex_unlock(&adc_mutex);
+
+    /* Convert to millivolts */
+    switch (channel)
+    {
+    case ADC_CHANNEL_VBUS:
+        return scale_adc_val(raw_val, VREF_MV, 174, 100);
+
+    case ADC_CHANNEL_BATTERY:
+        return scale_adc_val(raw_val, VREF_MV, 174, 390);
+
+    default:
+        return 0;
+    }
+}
diff --git a/firmware/target/arm/stm32/echoplayer/adc-target.h b/firmware/target/arm/stm32/echoplayer/adc-target.h
index 6c0eafc463..5edc098b37 100644
--- a/firmware/target/arm/stm32/echoplayer/adc-target.h
+++ b/firmware/target/arm/stm32/echoplayer/adc-target.h
@@ -21,4 +21,8 @@
 #ifndef __ECHOPLAYER_ADC_TARGET_H__
 #define __ECHOPLAYER_ADC_TARGET_H__
 
+/* ADC3 channels */
+#define ADC_CHANNEL_VBUS        11
+#define ADC_CHANNEL_BATTERY     16  /* real battery voltage */
+
 #endif /* __ECHOPLAYER_ADC_TARGET_H__ */
diff --git a/firmware/target/arm/stm32/echoplayer/clock-echoplayer.c b/firmware/target/arm/stm32/echoplayer/clock-echoplayer.c
index 1e2be5cd5c..d9bd0d31c5 100644
--- a/firmware/target/arm/stm32/echoplayer/clock-echoplayer.c
+++ b/firmware/target/arm/stm32/echoplayer/clock-echoplayer.c
@@ -165,6 +165,7 @@ INIT_ATTR static void init_periph_clock(void)
     reg_writef(RCC_D1CCIPR, SDMMCSEL_V(PLL1Q));
     reg_writef(RCC_D2CCIP1R, SAI1SEL_V(PLL2P), SPI45SEL_V(HSE));
     reg_writef(RCC_D2CCIP2R, I2C123SEL_V(HSI));
+    reg_writef(RCC_D3CCIPR, ADCSEL_V(PLL3R));
 
     /* Enable AXI SRAM in sleep mode to allow DMA'ing out of it */
     reg_writef(RCC_AHB3LPENR, AXISRAMEN(1));
diff --git a/firmware/target/arm/stm32/echoplayer/gpio-target.h b/firmware/target/arm/stm32/echoplayer/gpio-target.h
index 2e92f249c8..36c5df281b 100644
--- a/firmware/target/arm/stm32/echoplayer/gpio-target.h
+++ b/firmware/target/arm/stm32/echoplayer/gpio-target.h
@@ -55,4 +55,7 @@
 
 #define GPIO_USB_VBUS               GPIO_PA(9)
 
+#define GPIO_ADC_VBAT               GPIO_PH(5)
+#define GPIO_ADC_VBUS               GPIO_PC(1)
+
 #endif /* __ECHOPLAYER_GPIO_TARGET_H__ */
diff --git a/firmware/target/arm/stm32/echoplayer/power-echoplayer.c b/firmware/target/arm/stm32/echoplayer/power-echoplayer.c
index 63bf173d33..bbe3c627e5 100644
--- a/firmware/target/arm/stm32/echoplayer/power-echoplayer.c
+++ b/firmware/target/arm/stm32/echoplayer/power-echoplayer.c
@@ -20,6 +20,7 @@
  ****************************************************************************/
 #include "power.h"
 #include "mutex.h"
+#include "adc.h"
 #include "gpio-stm32h7.h"
 #include "system-echoplayer.h"
 #include "regs/cortex-m/cm_scb.h"
@@ -130,5 +131,5 @@ bool charging_state(void)
 
 int _battery_voltage(void)
 {
-    return 4000;
+    return adc_read(ADC_CHANNEL_BATTERY);
 }
diff --git a/firmware/target/arm/stm32/echoplayer/system-echoplayer.c b/firmware/target/arm/stm32/echoplayer/system-echoplayer.c
index 04e2a563ba..29d017eec9 100644
--- a/firmware/target/arm/stm32/echoplayer/system-echoplayer.c
+++ b/firmware/target/arm/stm32/echoplayer/system-echoplayer.c
@@ -49,6 +49,7 @@
 #define F_LCD_AF9    GPIOF_FUNCTION(9, GPIO_TYPE_PUSH_PULL, GPIO_SPEED_MEDIUM, GPIO_PULL_DISABLED)
 #define F_LPTIM4_OUT GPIOF_FUNCTION(3, GPIO_TYPE_PUSH_PULL, GPIO_SPEED_LOW, GPIO_PULL_DISABLED)
 #define F_LPTIM1_OUT GPIOF_FUNCTION(1, GPIO_TYPE_PUSH_PULL, GPIO_SPEED_VERYHIGH, GPIO_PULL_DISABLED)
+#define F_ANALOG     GPIOF_ANALOG()
 
 #if STM32H743_USBOTG_INSTANCE == STM32H743_USBOTG_INSTANCE_USB1
 # define F_OTG_FS   GPIOF_ANALOG()
@@ -90,6 +91,8 @@ static const struct gpio_setting gpios[] = {
     STM_DEFGPIO(GPIO_LCD_RESET,         F_OUT_LS(0)), /* active low */
     STM_DEFGPIO(GPIO_BACKLIGHT,         F_LPTIM1_OUT),
     STM_DEFGPIO(GPIO_USB_VBUS,          F_INPUT),     /* active high */
+    STM_DEFGPIO(GPIO_ADC_VBAT,          F_ANALOG),
+    STM_DEFGPIO(GPIO_ADC_VBUS,          F_ANALOG),
 };
 
 /* TODO - replace hex constants - there are probably mistakes here */
-- 
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