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Implement PIN_STATE command: Only set pins to output when requested #12

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Implement PIN_STATE command: Only set pins to output when requested #12

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5 changes: 5 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,11 @@ Dump a flashchip:
flashrom -p serprog:dev=/dev/ttyACM0:115200,spispeed=12M -r foo.bin
```

pico-serprog only switches the pins to output when requested by flashrom. This
means that you can leave your pico-serprog programmer attached to the flash;
you don't have to detach it before booting the board that you're programming.


## License

The project is based on the spi_flash example by Raspberry Pi (Trading) Ltd. which is licensed under BSD-3-Clause.
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14 changes: 11 additions & 3 deletions main.c
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Expand Up @@ -79,7 +79,14 @@ void putu32(uint32_t d) {

unsigned char write_buffer[4096];

void apply_pin_state(const pio_spi_inst_t *spi, bool state) {
pio_spi_enable_outputs(spi->pio, spi->sm, state, PIN_SCK, PIN_MOSI, PIN_MISO);
gpio_set_dir(PIN_CS, state? GPIO_OUT : GPIO_IN);
}

void process(const pio_spi_inst_t *spi, int command) {
static bool pin_state = false;

switch(command) {
case S_CMD_NOP:
putchar(S_ACK);
Expand Down Expand Up @@ -155,14 +162,15 @@ void process(const pio_spi_inst_t *spi, int command) {
if (freq >= 1) {
putchar(S_ACK);
putu32(serprog_spi_init(freq));
apply_pin_state(spi, pin_state);
} else {
putchar(S_NAK);
}
}
break;
case S_CMD_S_PIN_STATE:
//TODO:
getchar();
pin_state = !!getchar();
apply_pin_state(spi, pin_state);
putchar(S_ACK);
break;
default:
Expand Down Expand Up @@ -227,7 +235,7 @@ int main() {
// Initialize CS
gpio_init(PIN_CS);
gpio_put(PIN_CS, 1);
gpio_set_dir(PIN_CS, GPIO_OUT);
gpio_set_dir(PIN_CS, GPIO_IN); // switch to output on S_CMD_S_PIN_STATE

spi_offset = pio_add_program(spi.pio, &spi_cpha0_program);
serprog_spi_init(1000000); // 1 MHz
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10 changes: 8 additions & 2 deletions pio/spi.pio
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Original file line number Diff line number Diff line change
Expand Up @@ -54,9 +54,9 @@ static inline void pio_spi_init(PIO pio, uint sm, uint prog_offs, uint n_bits,
sm_config_set_in_shift(&c, false, true, n_bits);
sm_config_set_clkdiv(&c, clkdiv);

// MOSI, SCK output are low, MISO is input
// MOSI, SCK output are low, MISO is input -- but we start in input mode
pio_sm_set_pins_with_mask(pio, sm, 0, (1u << pin_sck) | (1u << pin_mosi));
pio_sm_set_pindirs_with_mask(pio, sm, (1u << pin_sck) | (1u << pin_mosi), (1u << pin_sck) | (1u << pin_mosi) | (1u << pin_miso));
pio_sm_set_pindirs_with_mask(pio, sm, 0, (1u << pin_sck) | (1u << pin_mosi) | (1u << pin_miso));
pio_gpio_init(pio, pin_mosi);
pio_gpio_init(pio, pin_miso);
pio_gpio_init(pio, pin_sck);
Expand All @@ -70,6 +70,12 @@ static inline void pio_spi_init(PIO pio, uint sm, uint prog_offs, uint n_bits,
pio_sm_init(pio, sm, prog_offs, &c);
pio_sm_set_enabled(pio, sm, true);
}

static inline void pio_spi_enable_outputs(PIO pio, uint sm, bool output, uint pin_sck, uint pin_mosi, uint pin_miso) {
uint mask = output? (1u << pin_sck) | (1u << pin_mosi) : 0;
pio_sm_set_pindirs_with_mask(pio, sm, mask, (1u << pin_sck) | (1u << pin_mosi) | (1u << pin_miso));
}

%}

; SPI with Chip Select
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