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machine/esp32xx: fix I2C NACK handling and controller hang after an address NACK #5774

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Merged
deadprogram merged 5 commits into from
Sep 28, 2026
Merged

machine/esp32xx: fix I2C NACK handling and controller hang after an address NACK #5774

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181dd97
machine/esp32xx: do not check ACK on I2C read commands
0hJonny Sep 28, 2026
c27fb30
machine/esp32xx: send the I2C address in its own WRITE command
0hJonny Sep 28, 2026
4f11705
machine/esp32xx: do not clock SCL when configuring I2C
0hJonny Sep 28, 2026
588bb6b
machine/esp32xx: read the last I2C byte in its own segment
0hJonny Sep 28, 2026
7ce6172
machine/esp32xx: reset the I2C FIFOs at the start of each transaction
0hJonny Sep 28, 2026
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50 changes: 35 additions & 15 deletions src/machine/machine_esp32xx_i2c.go
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Original file line number Diff line number Diff line change
Expand Up @@ -139,26 +139,23 @@ func (i2c *I2C) startMaster() {
func (i2c *I2C) resetMaster() {
// reset FSM
i2c.Bus.SetCTR_FSM_RST(1)
// clear the bus
i2c.Bus.SetSCL_SP_CONF_SCL_RST_SLV_NUM(9)
i2c.Bus.SetSCL_SP_CONF_SCL_RST_SLV_EN(1)
// No bus clear (SCL_RST_SLV), a GT911 did not ACK the next transaction after it.
// ESP-IDF does not clear the bus on init either https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L673
i2c.Bus.SetSCL_STRETCH_CONF_SLAVE_SCL_STRETCH_EN(1)
i2c.Bus.SetCTR_CONF_UPGATE(1)
i2c.Bus.FILTER_CFG.Set(0x377)
// wait for SCL_RST_SLV_EN
for i2c.Bus.GetSCL_SP_CONF_SCL_RST_SLV_EN() != 0 {
}
i2c.Bus.SetSCL_SP_CONF_SCL_RST_SLV_NUM(0)
}

type i2cCommandType = uint32
type i2cAck = uint32

// READ commands have no ack_check_en, with it a successful read raises NACK_INT.
// Same as ESP-IDF https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L1227
const (
i2cCMD_RSTART i2cCommandType = 6 << 11
i2cCMD_WRITE i2cCommandType = 1<<11 | 1<<8 // WRITE + ack_check_en
i2cCMD_READ i2cCommandType = 3<<11 | 1<<8 // READ + ack_check_en
i2cCMD_READLAST i2cCommandType = 3<<11 | 5<<8 // READ + ack_check_en + NACK
i2cCMD_WRITE i2cCommandType = 1<<11 | 1<<8 // WRITE + ack_check_en
i2cCMD_READ i2cCommandType = 3 << 11 // READ
i2cCMD_READLAST i2cCommandType = 3<<11 | 1<<10 // READ + NACK
i2cCMD_STOP i2cCommandType = 2 << 11
i2cCMD_END i2cCommandType = 4 << 11
)
Expand All @@ -174,6 +171,12 @@ func nanotime() int64

func (i2c *I2C) transmit(addr uint16, cmd []i2cCommand, timeoutMS int) error {
const intMask = esp.I2C_INT_STATUS_END_DETECT_INT_ST_Msk | esp.I2C_INT_STATUS_TRANS_COMPLETE_INT_ST_Msk | esp.I2C_INT_STATUS_TIME_OUT_INT_ST_Msk | esp.I2C_INT_STATUS_NACK_INT_ST_Msk
// Reset the FIFOs, bytes left after a NACK would go out in the next transaction.
// Same as ESP-IDF https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L1456
i2c.Bus.SetFIFO_CONF_TX_FIFO_RST(1)
i2c.Bus.SetFIFO_CONF_TX_FIFO_RST(0)
i2c.Bus.SetFIFO_CONF_RX_FIFO_RST(1)
i2c.Bus.SetFIFO_CONF_RX_FIFO_RST(0)
i2c.Bus.INT_CLR.SetBits(intMask)
i2c.Bus.INT_ENA.SetBits(intMask)
i2c.Bus.SetCTR_CONF_UPGATE(1)
Expand All @@ -186,7 +189,6 @@ func (i2c *I2C) transmit(addr uint16, cmd []i2cCommand, timeoutMS int) error {
timeoutNS := int64(timeoutMS) * 1000000
needAddress := true
needRestart := false
readLast := false
var readTo []byte
for cmdIdx, reg := 0, &i2c.Bus.COMD0; cmdIdx < len(cmd); {
c := &cmd[cmdIdx]
Expand All @@ -200,11 +202,16 @@ func (i2c *I2C) transmit(addr uint16, cmd []i2cCommand, timeoutMS int) error {
case i2cCMD_WRITE:
count := 32
if needAddress {
// Own WRITE plus END for the address, else an address NACK hangs the controller.
// Same as ESP-IDF https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L1296
needAddress = false
i2c.Bus.SetDATA_FIFO_RDATA((uint32(addr) & 0x7f) << 1)
count--
i2c.Bus.SLAVE_ADDR.Set(uint32(addr))
i2c.Bus.SetCTR_CONF_UPGATE(1)
reg.Set(i2cCMD_WRITE | 1)
reg = nextAddress(reg)
reg.Set(i2cCMD_END)
reg = nil
break
}
for ; count > 0 && c.head < len(c.data); count, c.head = count-1, c.head+1 {
i2c.Bus.SetDATA_FIFO_RDATA(uint32(c.data[c.head]))
Expand All @@ -222,11 +229,15 @@ func (i2c *I2C) transmit(addr uint16, cmd []i2cCommand, timeoutMS int) error {

case i2cCMD_READ:
if needAddress {
// Own WRITE plus END for the address, see i2cCMD_WRITE above.
needAddress = false
i2c.Bus.SetDATA_FIFO_RDATA((uint32(addr)&0x7f)<<1 | 1)
i2c.Bus.SLAVE_ADDR.Set(uint32(addr))
reg.Set(i2cCMD_WRITE | 1)
reg = nextAddress(reg)
reg.Set(i2cCMD_END)
reg = nil
break
}
if needRestart {
// We need to send RESTART again after i2cCMD_WRITE.
Expand All @@ -249,12 +260,21 @@ func (i2c *I2C) transmit(addr uint16, cmd []i2cCommand, timeoutMS int) error {
if bytes > 32 {
bytes = 32
}
if split && bytes > 0 {
// Last byte in its own segment, else 64 and 96 byte reads time out.
// Same as ESP-IDF https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L1259
reg.Set(i2cCMD_READ | uint32(bytes))
reg = nextAddress(reg)
reg.Set(i2cCMD_END)
readTo = c.data[c.head : c.head+bytes]
reg = nil
break
}
if bytes > 0 {
reg.Set(i2cCMD_READ | uint32(bytes))
reg = nextAddress(reg)
}
if split {
readLast = true
reg.Set(i2cCMD_READLAST | 1)
reg = nextAddress(reg)
readTo = c.data[c.head : c.head+bytes+1] // read bytes + 1 last byte
Expand Down Expand Up @@ -285,7 +305,7 @@ func (i2c *I2C) transmit(addr uint16, cmd []i2cCommand, timeoutMS int) error {
}
}
switch {
case mask&esp.I2C_INT_STATUS_NACK_INT_ST_Msk != 0 && !readLast:
case mask&esp.I2C_INT_STATUS_NACK_INT_ST_Msk != 0:
return errI2CAckExpected
case mask&esp.I2C_INT_STATUS_TIME_OUT_INT_ST_Msk != 0:
if readTo != nil {
Expand Down
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