General Note GCC 

The latest version of Pi OS only supplies GCC 8.3 in a bare metal compiler configuration arm-none-eabi and this is the Kit you should select.

The alternative 10.2 targets Linux and cannot be used to compile Pico programs.

Windows 10 currently supplies 10.3 arm-none-eabi for bare metal targets.

General Note RDP

The latest version of Pi OS needs some tweeking to make Windows remote desktop work.

See the article on I Programmer - Remote Desktop To A Headless Pi Running Bullseye

Page 25:

the instruction should read:   "git submodule update --init"  (minus minus init, instead of minus init minus: "-init-")

Page 27

before moving on :

becomes

before moving on by clicking on the "four little square" icon in the column at the left of the screen, as shown on the picture below. 

Page 30:

Page 41

Page 46

This uses the same CmakeLists.txt file as blinky in the previous chapter and the same launch.json file. The only difference is that now we are using GP22.

to

This uses the same CMakeLists.txt file as blinky in the previous chapter and the same launch.json file. The only difference is that now we are using GP22.

 i.e. change m to M

Page 61

As the internal pull-down resistor is used, the switch can be connected to the line and ground without any external resistors:

should read:

As the internal pull-up resistor is used, the switch can be connected to the line and ground without any external resistors:

Page 64:

Change

An LED is a non-linear electronic component – the voltage across is stays more or less the same irrespective of the current passing through the device.

to

An LED is a non-linear electronic component – the voltage across it stays more or less the same irrespective of the current passing through the device.

Page 67:

Change

From its datasheet you can discover that the max collector current is 800mA and beta is at least 50, which makes it suitable for driving a 20mA LED with a GPIO current of at most 20/50mA = 0.4mA. 

to

From its datasheet you can discover that the max collector current is 800mA and beta is at least 50, which makes it suitable for driving a 20mA LED with a GPIO current of at most 20mA/50 = 0.4mA, where 50 is the HFE or beta.

Page 68:

Assuming a forward voltage drop of 1.6V and a current of 20mA the resistor is given by (3.3-1.6)/20kΩ = 85Ω. In practice, we could use anything in the range 82Ω to 100Ω.

to

Assuming a forward voltage drop of 1.6V and a current of 20mA the resistor is given by (3.3-1.6)V/20mA = 85Ω.

Page 76:

change

Vout = V R2/(R1+R2)

to

Vout = V * R2/(R1+R2)

Page 81:

change

As the internal pull-down resistor is used, the switch can be connected to the line and ground without any external resistors:

to

As the internal pull-upresistor is used, the switch can be connected to the line and ground without any external resistors:

Page 98:

Change

Notice that an event, or an event queue, cannot increase the program’s throughput or its latency – the time to react to an input.

to

Notice that an event, or an event queue, cannot increase the program’s throughput or decrease its latency – the time to react to an input.

Page 113:

change

Of course, even though the PWM line can generate pulses very fast pulses, usually what you want to do is change the nature of the pulses and this is a slower process involving the processor.

to

Of course, even though the PWM line can generate very fast pulses, usually what you want to do is change the nature of the pulses and this is a slower process involving the processor.

target_link_libraries(myprogram  pico_stdlib
                               hardware_gpio hardware_pwm)

target_link_libraries(myprogram  pico_stdlib
                               hardware_gpio hardware_pwm)

target_link_libraries(myprogram  pico_stdlib
                               hardware_gpio hardware_pwm)

Page 131

The line in the first new paragraph:

The PWM output in this configuration mimics the workings of an 8-bit A-to-D converter.

shoudl read:

The PWM output in this configuration mimics the workings of an 8-bit D-to-A converter.

i.e. swap A and D.

Page 135

The graph axis labels need to be switched.

Page 155:

Function "void BiMotorspeed()" - At the top of the page, are you sure "m->forward = true" must be "= true" in the two cases of the "if" statement ? Shouldn't the second be "false" ?

Page 167

So for example, if we use GP28 as the first GPIO line the four lines are GP18, GP19, GP20 and GP21 and the first element of stepTable sets just GP21 to high.

should read

So for example, if we use GP18 as the first GPIO line the four lines are GP18, GP19, GP20 and GP21 and the first element of stepTable sets just GP21 to high.

i.e. change GP28 to GP18

Page 171

the rotation is in rotations per second not per minute - I forgot to multiply by 60.

It should read:

In this case, H‑bridge GP21 is A, GP20 is B, GP19 is A- and GP18 is B-. The stepping speed is such that a 200-step motor, i.e. 400 half steps, will rotate in 400*1 ms= 0.4 s, i.e. 2.5 rps (revolutions per second), which is a good starting speed. Decrease the sleep time for a higher speed. 

The error is also on:page 173

Page 172:

change

The second cancels a timer.

to

The third cancels a timer.

Page 173

Notice that we have to deal with the case of speed set to zero separately to avoid a divide by zero exception. The speed is specified in rps *100. So setting speed to 250 gives a rotation of 2.5rps.

Page 182:

There are 3 references to MSIO on the page they should be changed MISO 

Page 187

Next we can send some data and receive it right back:

uint8_t read_data = bcm2835_spi_transfer(0xAA);

 remove the program line and change the : to ;

Next we can send some data and receive it right back.

Page 188:

Change  MSIO  to MISO

Page 188 

If you connect a logic analyzer to the three pins involved – 4, 6 and 7, you will see the data transfer:

 change to:

If you connect a logic analyzer to the three GPIO lines involved – 4, 6 and 7, you will see the data transfer:

 i.e change pins to GPIO lines

Page 229

Temperature in °C= -46.85 + 175.72 * data16 / 216

change to

Temperature in °C= -46.85 + 175.72 * data16 / 2¹⁶ 

change 216 to 2¹⁶

Page 230

RH= -6 + 125 * data16 / 216

change to 

RH= -6 + 125 * data16 / 2¹⁶

change 216 to 2¹⁶

Page 241:

change

The complete program is but remember that it needs the PIO program and the CMakeLists.txt file:

to

The complete program is listed below, but remember that it needs the PIO program and the CMakeLists.txt file:

Page 243

You can use the registers to implement a for loop with up to 32 repeats. The jmp instruction can test the value of a register for zero and auto-decrement it after the test. This means an n repeat for loop can be constructed as:

set x,n
loop: nop
jump x--, loop

Using this you can slow the rate at which the GPIO line is toggled by repeating the nop 32 times. However, even if you use:

set x,n
loop: nop [31]
jump x--, loop

the effective rate of toggling the GPIO line is still too great to see an LED flash. To slow it down even more you need two nested loops.

change to

You can use the registers to implement a for loop with up to 32 repeats. The jmp instruction can test the value of a register for zero and auto-decrement it after the test. This means an n repeat for loop can be constructed as:

set x,n
loop: nop
jmp x--, loop

Using this you can slow the rate at which the GPIO line is toggled by repeating the nop 32 times. However, even if you use:

set x,n
loop: nop [31]
jmp x--, loop

the effective rate of toggling the GPIO line is still too great to see an LED flash. To slow it down even more you need two nested loops.

i.e. change jump to jmp

Page 247

This seems simple, but the set pindir is more complicated than you might expect. The set instruction sets the direction of the SET group of pins. The literal value used in the instruction is used as a mask to set the pin directions. This means that it can only set the direction of the first five GPIO lines in the SET group. This usually isn’t a problem as using more than five GPIO lines for output is uncommon. However, the out instruction sends the data from the OSR to the first two GPIO lines in the OUT group, not the SET group. You can see that the set instruction only enables the first two lines of the OUT group if they are the same in both groups.

change to 

This seems simple, but the set pindirs is more complicated than you might expect. The set instruction sets the direction of the SET group of pins. The literal value used in the instruction is used as a mask to set the pin directions. This means that it can only set the direction of the first five GPIO lines in the SET group. This usually isn’t a problem as using more than five GPIO lines for output is uncommon. However, the out instruction sends the data from the OSR to the first two GPIO lines in the OUT group, not the SET group. You can see that the set instruction only enables the first two lines of the OUT group if they are the same in both groups.

i.e. pindir -> pindirs

Page 253

sm_config_set_sideset_pins(&c,2);
pio_gpio_init(pio0, 2);
pio_gpio_init(pio0, 3);

The first instruction has to be changed to:

pio_sm_set_consecutive_pindirs(pio0,sm,2,2,true);

Page 300

change 

The complete program to read and display the temperature is:
#include 
#include "pico/stdlib.h"
#include "hardware/gpio.h"

int presence(uint8_t pin)
{
 gpio_set_dir(2, GPIO_OUT);
 gpio_put(pin, 1);
 sleep_ms(1);
 gpio_put(pin, 0);
 sleep_us(480);
 gpio_set_dir(pin, GPIO_IN);
 sleep_us(70);
 int b = gpio_get(pin);
 sleep_us(410);
 return b;
}

To

The complete program to read and display the temperature is:

#include 
#include "pico/stdlib.h"
#include "hardware/gpio.h"

int presence(uint8_t pin)
{
 gpio_set_dir(pin, GPIO_OUT);
 gpio_put(pin, 1);
 sleep_ms(1);
 gpio_put(pin, 0);
 sleep_us(480);
 gpio_set_dir(pin, GPIO_IN);
 sleep_us(70);
 int b = gpio_get(pin);
 sleep_us(410);
 return b;
}

i.e. change 2 to pin in first line of function.

Page 336

int getBlocks(uint8_t buf[], int len, int num, char target[])
{
 for (int i = 0; i < num; i++)
 {
        if (uart_is_readable_within_us(uart1, 1000 * 1000));
        getBlock(buf, len);
        if (strstr(buf, target))
            return i;
    }
    return -1;
}

change to:

int getBlocks(uint8_t buf[], int len, int num, char target[])
{
 for (int i = 0; i < num; i++)
 {
        if (uart_is_readable_within_us(uart1, 1000 * 1000))
        {
            getBlock(buf, len);
            if (strstr(buf, target))
                return i;
        }
  }
    return -1;
}

i.e. add {} around if  body.

Page 330 and 345:

change

uart_set_translate_crlf(uart0,true);

to

uart_set_translate_crlf(uart1,true);